net10, the refactor finished, and federation that works

The tree had not compiled since its first commit: Group, DmGroup and
IGroupUsersService were referenced and never written, an IDE rename had
turned the user-settings DTO into the ViewAvatarServer enum, and the settings
were saved as an entity they no longer were.

Built now:
- Group (an ActivityPub Group actor with its own keys, members, invitation
  code and optional password) and DmGroup (a conversation), with
  /clientapi/group/{list,insert,update,join,leave,approve}.
- Posts and DMs: /clientapi/post/{list,insert,delete}, /clientapi/dm/{list,insert};
  DM recipients are local usernames or user@host handles resolved by WebFinger.
- Invitation sign-up and login against the group's invitation code, checking
  the password before any account is created.
- Federation: WebFinger, NodeInfo 2.0, actors at /peasants/{name} (Person,
  Group, and an Application instance actor) with SPKI keys, draft-cavage
  RSA-SHA256 HTTP signatures both ways, an inbox handling Follow (+Accept),
  Undo, Create, Delete and Update, an outbox, notes at /posts/{id}, and a
  persisted, retried, signed delivery queue. A post to a group is announced
  by the group to its followers (FEP-1b12).
- The unused, broken typed ActivityPub models are replaced by a renderer;
  NSign's HMAC setup, which could not federate, is gone.

Upgrade: net10.0, MongoDB.Entities 25.1 (instance DB API, Standard GUIDs),
Swashbuckle 10 / OpenApi 2, Serilog.AspNetCore 10, MailKit 4.18,
PasswordGenerator 3. The JWT keys are 64 bytes (IdentityModel 8 refuses
shorter for HS512). Production runs its own mongod on 127.0.0.1:27022, as
Sintopia's apps do, and deploys to privapub.thepra.dev from the build runner.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012CzABvBkbcFqoHdmi8b9WB

PrivaPub.ClientModels/Group/InsertGroupForm.cs

@@ -0,0 +1,30 @@
+using PrivaPub.ClientModels.Resources;
+using PrivaPub.ClientModels.ValidatorAttributes;
+
+using System.ComponentModel.DataAnnotations;
+
+namespace PrivaPub.ClientModels.Group
+{
+	public class InsertGroupForm
+	{
+		[Required(ErrorMessageResourceName = "Required", ErrorMessageResourceType = typeof(ErrorsResource))]
+		public string AvatarId { get; set; }
+
+		[Required(ErrorMessageResourceName = "Required", ErrorMessageResourceType = typeof(ErrorsResource)),
+			StringLength(32, MinimumLength = 3, ErrorMessageResourceName = "StringLengthMinMax", ErrorMessageResourceType = typeof(ErrorsResource)),
+			RegularExpression("^[a-z0-9_]+$", ErrorMessageResourceName = "EmptySpacesNotAllowed", ErrorMessageResourceType = typeof(ErrorsResource)),
+			NoWhiteSpaces]
+		public string UserName { get; set; }
+
+		[Required(ErrorMessageResourceName = "Required", ErrorMessageResourceType = typeof(ErrorsResource)),
+			StringLength(64, ErrorMessageResourceName = "MaxLengthString", ErrorMessageResourceType = typeof(ErrorsResource))]
+		public string Name { get; set; }
+
+		[StringLength(2000, ErrorMessageResourceName = "MaxLengthString", ErrorMessageResourceType = typeof(ErrorsResource))]
+		public string Description { get; set; }
+
+		public string InvitationPassword { get; set; }
+		public bool IsDiscoverable { get; set; } = true;
+		public bool ManuallyApprovesMembers { get; set; }
+	}
+}

PrivaPub.ClientModels/Group/JoinGroupForm.cs

@@ -0,0 +1,28 @@
+using PrivaPub.ClientModels.Resources;
+
+using System.ComponentModel.DataAnnotations;
+
+namespace PrivaPub.ClientModels.Group
+{
+	public class JoinGroupForm
+	{
+		[Required(ErrorMessageResourceName = "Required", ErrorMessageResourceType = typeof(ErrorsResource))]
+		public string AvatarId { get; set; }
+
+		[Required(ErrorMessageResourceName = "Required", ErrorMessageResourceType = typeof(ErrorsResource)),
+			StringLength(Constants.GroupInvitationLength, MinimumLength = Constants.GroupInvitationLength,
+				ErrorMessageResourceName = "StringLengthMinMax", ErrorMessageResourceType = typeof(ErrorsResource))]
+		public string InvitationCode { get; set; }
+
+		public string InvitationPassword { get; set; }
+	}
+
+	public class GroupMembershipForm
+	{
+		[Required(ErrorMessageResourceName = "Required", ErrorMessageResourceType = typeof(ErrorsResource))]
+		public string AvatarId { get; set; }
+		[Required(ErrorMessageResourceName = "Required", ErrorMessageResourceType = typeof(ErrorsResource))]
+		public string GroupId { get; set; }
+		public string MemberActorURI { get; set; }
+	}
+}

PrivaPub.ClientModels/Group/UpdateGroupForm.cs

@@ -0,0 +1,25 @@
+using PrivaPub.ClientModels.Resources;
+
+using System.ComponentModel.DataAnnotations;
+
+namespace PrivaPub.ClientModels.Group
+{
+	public class UpdateGroupForm
+	{
+		[Required(ErrorMessageResourceName = "Required", ErrorMessageResourceType = typeof(ErrorsResource))]
+		public string AvatarId { get; set; }
+		[Required(ErrorMessageResourceName = "Required", ErrorMessageResourceType = typeof(ErrorsResource))]
+		public string GroupId { get; set; }
+
+		[StringLength(64, ErrorMessageResourceName = "MaxLengthString", ErrorMessageResourceType = typeof(ErrorsResource))]
+		public string Name { get; set; }
+		[StringLength(2000, ErrorMessageResourceName = "MaxLengthString", ErrorMessageResourceType = typeof(ErrorsResource))]
+		public string Description { get; set; }
+
+		public string InvitationPassword { get; set; }
+		public bool RemoveInvitationPassword { get; set; }
+		public bool RegenerateInvitationCode { get; set; }
+		public bool? IsDiscoverable { get; set; }
+		public bool? ManuallyApprovesMembers { get; set; }
+	}
+}

PrivaPub.ClientModels/Group/ViewGroup.cs

@@ -0,0 +1,19 @@
+namespace PrivaPub.ClientModels.Group
+{
+	public class ViewGroup
+	{
+		public string Id { get; set; }
+		public string UserName { get; set; }
+		public string Name { get; set; }
+		public string Description { get; set; }
+		public string Url { get; set; }
+		public string Handle { get; set; }
+		public bool IsDiscoverable { get; set; }
+		public bool ManuallyApprovesMembers { get; set; }
+		public bool IsOwner { get; set; }
+		public string InvitationCode { get; set; }
+		public bool IsPasswordRequired { get; set; }
+		public int MembersCount { get; set; }
+		public DateTime CreationDate { get; set; }
+	}
+}