chore: upgrade AvatarTheme

* `AvatarTheme` is now an `InheritedTheme` and has a corresponding `AvatarThemeData` class

packages/stream_chat_flutter/lib/src/theme/avatar_theme.dart

@@ -1,9 +1,62 @@
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
+import 'package:stream_chat_flutter/src/stream_chat_theme.dart';
+import 'package:stream_chat_flutter/src/theme/themes.dart';
 
-/// Theme for avatar
-class AvatarTheme {
-  /// Constructor for creating [AvatarTheme]
-  AvatarTheme({
+/// Overrides the default style of [UserAvatar] descendants.
+///
+/// See also:
+///
+///  * [AvatarThemeData], which is used to configure this theme.
+class AvatarTheme extends InheritedTheme {
+  /// Creates an [AvatarTheme].
+  ///
+  /// The [data] parameter must not be null.
+  const AvatarTheme({
+    Key? key,
+    required this.data,
+    required Widget child,
+  }) : super(key: key, child: child);
+
+  /// The configuration of this theme.
+  final AvatarThemeData data;
+
+  /// The closest instance of this class that encloses the given context.
+  ///
+  /// If there is no enclosing [GalleryHeaderTheme] widget, then
+  /// [StreamChatThemeData.avatarTheme] is used.
+  ///
+  /// Typical usage is as follows:
+  ///
+  /// ```dart
+  /// final theme = AvatarTheme.of(context);
+  /// ```
+  static AvatarThemeData of(BuildContext context) {
+    final avatarTheme =
+        context.dependOnInheritedWidgetOfExactType<AvatarTheme>();
+    return avatarTheme?.data ?? StreamChatTheme.of(context).avatarTheme;
+  }
+
+  @override
+  Widget wrap(BuildContext context, Widget child) =>
+      AvatarTheme(data: data, child: child);
+
+  @override
+  bool updateShouldNotify(AvatarTheme oldWidget) => data != oldWidget.data;
+}
+
+/// A style that overrides the default appearance of [UserAvatar]s when used
+/// with [AvatarTheme] or with the overall [StreamChatTheme]'s
+/// [StreamChatThemeData.avatarTheme].
+///
+/// See also:
+///
+/// * [AvatarTheme], the theme which is configured with this class.
+/// * [StreamChatThemeData.avatarTheme], which can be used to override
+/// the default style for [UserAvatar]s below the overall [StreamChatTheme].
+class AvatarThemeData with Diagnosticable {
+  /// Creates an [AvatarThemeData].
+  AvatarThemeData({
     BoxConstraints? constraints,
     BorderRadius? borderRadius,
   })  : _constraints = constraints,
@@ -15,30 +68,62 @@ class AvatarTheme {
   /// Get constraints for avatar
   BoxConstraints get constraints =>
       _constraints ??
-          const BoxConstraints.tightFor(
-            height: 32,
-            width: 32,
-          );
+      const BoxConstraints.tightFor(
+        height: 32,
+        width: 32,
+      );
 
   /// Get border radius
   BorderRadius get borderRadius => _borderRadius ?? BorderRadius.circular(20);
 
-  /// Copy with another theme
-  AvatarTheme copyWith({
+  /// Copy this [AvatarThemeData] to another.
+  AvatarThemeData copyWith({
     BoxConstraints? constraints,
     BorderRadius? borderRadius,
   }) =>
-      AvatarTheme(
+      AvatarThemeData(
         constraints: constraints ?? _constraints,
         borderRadius: borderRadius ?? _borderRadius,
       );
 
-  /// Merge with another AvatarTheme
-  AvatarTheme merge(AvatarTheme? other) {
+  /// Linearly interpolate between two [UserAvatar] themes.
+  ///
+  /// All the properties must be non-null.
+  AvatarThemeData lerp(
+    AvatarThemeData a,
+    AvatarThemeData b,
+    double t,
+  ) =>
+      AvatarThemeData(
+        borderRadius: BorderRadius.lerp(a.borderRadius, b.borderRadius, t),
+        constraints: BoxConstraints.lerp(a.constraints, b.constraints, t),
+      );
+
+  @override
+  bool operator ==(Object other) =>
+      identical(this, other) ||
+      other is AvatarThemeData &&
+          runtimeType == other.runtimeType &&
+          _constraints == other._constraints &&
+          _borderRadius == other._borderRadius;
+
+  @override
+  int get hashCode => _constraints.hashCode ^ _borderRadius.hashCode;
+
+  /// Merges one [AvatarThemeData] with the another
+  AvatarThemeData merge(AvatarThemeData? other) {
     if (other == null) return this;
     return copyWith(
       constraints: other._constraints,
       borderRadius: other._borderRadius,
     );
   }
-}
+
+  @override
+  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+    super.debugFillProperties(properties);
+    properties
+      ..add(DiagnosticsProperty('borderRadius', borderRadius))
+      ..add(DiagnosticsProperty('constraints', constraints));
+  }
+}

packages/stream_chat_flutter/lib/src/theme/channel_header_theme.dart

@@ -18,7 +18,7 @@ class ChannelHeaderTheme {
   final TextStyle? subtitle;
 
   /// Theme for avatar
-  final AvatarTheme? avatarTheme;
+  final AvatarThemeData? avatarTheme;
 
   /// Color for [ChannelHeaderTheme]
   final Color? color;
@@ -27,7 +27,7 @@ class ChannelHeaderTheme {
   ChannelHeaderTheme copyWith({
     TextStyle? title,
     TextStyle? subtitle,
-    AvatarTheme? avatarTheme,
+    AvatarThemeData? avatarTheme,
     Color? color,
   }) =>
       ChannelHeaderTheme(

packages/stream_chat_flutter/lib/src/theme/channel_list_header_theme.dart

@@ -14,7 +14,7 @@ class ChannelListHeaderTheme {
   final TextStyle? title;
 
   /// Theme dedicated to the userAvatar
-  final AvatarTheme? avatarTheme;
+  final AvatarThemeData? avatarTheme;
 
   /// Background color of the appbar
   final Color? color;
@@ -22,7 +22,7 @@ class ChannelListHeaderTheme {
   /// Returns a new [ChannelListHeaderTheme] replacing some of its properties
   ChannelListHeaderTheme copyWith({
     TextStyle? title,
-    AvatarTheme? avatarTheme,
+    AvatarThemeData? avatarTheme,
     Color? color,
   }) =>
       ChannelListHeaderTheme(

packages/stream_chat_flutter/lib/src/theme/channel_preview_theme.dart

@@ -23,7 +23,7 @@ class ChannelPreviewTheme {
   final TextStyle? lastMessageAt;
 
   /// Avatar theme
-  final AvatarTheme? avatarTheme;
+  final AvatarThemeData? avatarTheme;
 
   /// Unread counter color
   final Color? unreadCounterColor;
@@ -36,7 +36,7 @@ class ChannelPreviewTheme {
     TextStyle? title,
     TextStyle? subtitle,
     TextStyle? lastMessageAt,
-    AvatarTheme? avatarTheme,
+    AvatarThemeData? avatarTheme,
     Color? unreadCounterColor,
     double? indicatorIconSize,
   }) =>

packages/stream_chat_flutter/lib/src/theme/gallery_header_theme.dart

@@ -8,7 +8,7 @@ import 'package:stream_chat_flutter/src/stream_chat_theme.dart';
 ///
 ///  * [GalleryHeaderThemeData], which is used to configure this theme.
 class GalleryHeaderTheme extends InheritedTheme {
-  /// Creates an [GalleryHeaderTheme].
+  /// Creates a [GalleryHeaderTheme].
   ///
   /// The [data] parameter must not be null.
   const GalleryHeaderTheme({

packages/stream_chat_flutter/lib/src/theme/message_theme.dart

@@ -49,7 +49,7 @@ class MessageTheme {
   final Color? reactionsMaskColor;
 
   /// Theme of the avatar
-  final AvatarTheme? avatarTheme;
+  final AvatarThemeData? avatarTheme;
 
   /// Copy with a theme
   MessageTheme copyWith({
@@ -60,7 +60,7 @@ class MessageTheme {
     TextStyle? replies,
     Color? messageBackgroundColor,
     Color? messageBorderColor,
-    AvatarTheme? avatarTheme,
+    AvatarThemeData? avatarTheme,
     Color? reactionsBackgroundColor,
     Color? reactionsBorderColor,
     Color? reactionsMaskColor,