Add group create post form

lib/models/group.dart

@@ -58,4 +58,10 @@ class Group {
       membershipLevel == GroupMembershipLevel.ADMINISTRATOR ||
       membershipLevel == GroupMembershipLevel.MODERATOR ||
       membershipLevel == GroupMembershipLevel.MEMBER;
+
+  bool get canCreatePost =>
+      membershipLevel == GroupMembershipLevel.ADMINISTRATOR ||
+      membershipLevel == GroupMembershipLevel.MODERATOR ||
+      (membershipLevel == GroupMembershipLevel.MEMBER &&
+          postCreationLevel == GroupPostCreationLevel.MEMBERS);
 }

lib/ui/screens/authorized_group_page_screen.dart

@@ -1,9 +1,11 @@
+import 'package:comunic/enums/post_target.dart';
 import 'package:comunic/helpers/posts_helper.dart';
 import 'package:comunic/models/advanced_group_info.dart';
 import 'package:comunic/ui/widgets/group_following_widget.dart';
 import 'package:comunic/ui/widgets/group_icon_widget.dart';
 import 'package:comunic/ui/widgets/group_membership_widget.dart';
 import 'package:comunic/ui/widgets/like_widget.dart';
+import 'package:comunic/ui/widgets/post_create_form_widget.dart';
 import 'package:comunic/ui/widgets/posts_list_widget.dart';
 import 'package:flutter/material.dart';
 
@@ -38,14 +40,20 @@ class _AuthorizedGroupPageScreenState extends State<AuthorizedGroupPageScreen> {
     return RefreshIndicator(
       onRefresh: () => widget.needRefresh(),
       child: ListView(
-        children: <Widget>[_buildGroupPageHeader(), _buildGroupPagePostsList()],
+        children: <Widget>[
+          _buildGroupPageHeader(),
+          _buildPostCreationArea(),
+          _buildGroupPagePostsList()
+        ],
       ),
     );
   }
 
   /// Build group page header
   Widget _buildGroupPageHeader() {
-    return Padding(
+    return Container(
+      color: Colors.black45,
+      child: Padding(
         padding: const EdgeInsets.all(8.0),
         child: Row(
           children: <Widget>[
@@ -80,9 +88,20 @@ class _AuthorizedGroupPageScreenState extends State<AuthorizedGroupPageScreen> {
             )
           ],
         ),
+      ),
     );
   }
 
+  /// Add create post target
+  Widget _buildPostCreationArea() {
+    if (!_group.canCreatePost) return Container();
+
+    return PostCreateFormWidget(
+        postTarget: PostTarget.GROUP_PAGE,
+        targetID: _group.id,
+        onCreated: () => widget.needRefresh());
+  }
+
   /// Build the list of posts of the group
   Widget _buildGroupPagePostsList() {
     return PostsListWidget(