Groups: make, join, run and leave communities and circles

The Groups page (/groups, in the menu) is where a persona makes a community
or a circle (with its invitation code and an optional password), joins one
by invitation and leaves one. For the groups it runs it edits them, shows
the invitation, lets in or declines the requests to join, and takes members
out, through PrivaPub's new /clientapi/group/members, reject and remove.
The e2e makes a circle, joins it as another persona with the code, and has
the owner take that member out.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

ClientJsonContext.cs

@@ -38,6 +38,12 @@ namespace decePubClient;
 [JsonSerializable(typeof(InsertAvatarForm))]
 [JsonSerializable(typeof(ViewGroup))]
 [JsonSerializable(typeof(List<ViewGroup>))]
+[JsonSerializable(typeof(ViewGroupMember))]
+[JsonSerializable(typeof(List<ViewGroupMember>))]
+[JsonSerializable(typeof(InsertGroupForm))]
+[JsonSerializable(typeof(UpdateGroupForm))]
+[JsonSerializable(typeof(JoinGroupForm))]
+[JsonSerializable(typeof(GroupMembershipForm))]
 [JsonSerializable(typeof(ViewPost))]
 [JsonSerializable(typeof(List<ViewPost>))]
 [JsonSerializable(typeof(InsertPostForm))]