FEATURE: introduces group channels (#24288)

Group channels will allow users to create channels with a name and invite people. It's possible to add people even after creation of the channel. Removing users is not yet possible but will be added in the near future.

Technically a group channel is `direct_message_channel` with a group attribute set to true on its direct message (chatable). This model might evolve in the future but offers much flexibility for now without having to rely on a complex migration.

The commit essentially consists of:
- a migration to set existing direct message channels with more than 2 users to a group
- a new message creator which allows to search, add members, and create groups
- a new `AddUsersToChannel` service
- a modified `SearchChatable` service

plugins/chat/spec/requests/chat/api/channels_memberships_controller_spec.rb

@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+RSpec.describe Chat::Api::ChannelsMembershipsController do
+  fab!(:current_user) { Fabricate(:user) }
+  fab!(:channel_1) do
+    Fabricate(:direct_message_channel, group: true, users: [current_user, Fabricate(:user)])
+  end
+
+  before do
+    SiteSetting.chat_enabled = true
+    SiteSetting.chat_allowed_groups = Group::AUTO_GROUPS[:everyone]
+    channel_1.add(current_user)
+    sign_in(current_user)
+  end
+
+  describe "#create" do
+    describe "success" do
+      it "works" do
+        add_users_to_channel(current_user, channel_1)
+        post "/chat/api/channels/#{channel_1.id}/memberships",
+             params: {
+               usernames: [Fabricate(:user).username],
+             }
+
+        expect(response.status).to eq(200)
+      end
+    end
+
+    context "when users can't be added" do
+      before { channel_1.chatable.update(group: false) }
+
+      it "returns a 422" do
+        post "/chat/api/channels/#{channel_1.id}/memberships",
+             params: {
+               usernames: [Fabricate(:user).username],
+             }
+
+        expect(response.status).to eq(422)
+        expect(response.parsed_body["errors"].first).to eq(
+          I18n.t("chat.errors.users_cant_be_added_to_channel"),
+        )
+      end
+    end
+
+    context "when channel is not found" do
+      before { channel_1.chatable.update!(group: false) }
+
+      it "returns a 404" do
+        get "/chat/api/channels/-999/messages", params: { usernames: [Fabricate(:user).username] }
+
+        expect(response.status).to eq(404)
+      end
+    end
+  end
+end

plugins/chat/spec/requests/chat/api/chatables_controller_spec.rb

@@ -14,13 +14,16 @@ RSpec.describe Chat::Api::ChatablesController do
     describe "without chat permissions" do
       it "errors errors for anon" do
         get "/chat/api/chatables"
+
         expect(response.status).to eq(403)
       end
 
       it "errors when user cannot chat" do
         SiteSetting.chat_allowed_groups = Group::AUTO_GROUPS[:staff]
         sign_in(current_user)
+
         get "/chat/api/chatables"
+
         expect(response.status).to eq(403)
       end
     end
@@ -28,9 +31,11 @@ RSpec.describe Chat::Api::ChatablesController do
     describe "with chat permissions" do
       fab!(:channel_1) { Fabricate(:chat_channel) }
 
-      before { sign_in(current_user) }
+      before { channel_1.add(current_user) }
 
       it "returns results" do
+        sign_in(current_user)
+
         get "/chat/api/chatables", params: { term: channel_1.name }
 
         expect(response.status).to eq(200)

plugins/chat/spec/requests/chat/api/direct_messages_controller_spec.rb

@@ -23,7 +23,10 @@ RSpec.describe Chat::Api::DirectMessagesController do
   describe "#create" do
     before { Group.refresh_automatic_groups! }
 
-    shared_examples "creating dms" do
+    describe "dm with one other user" do
+      let(:usernames) { user1.username }
+      let(:direct_message_user_ids) { [current_user.id, user1.id] }
+
       it "creates a new dm channel with username(s) provided" do
         expect {
           post "/chat/api/direct-message-channels.json", params: { target_usernames: [usernames] }
@@ -35,31 +38,55 @@ RSpec.describe Chat::Api::DirectMessagesController do
 
       it "returns existing dm channel if one exists for username(s)" do
         create_dm_channel(direct_message_user_ids)
+
         expect {
           post "/chat/api/direct-message-channels.json", params: { target_usernames: [usernames] }
         }.not_to change { Chat::DirectMessage.count }
       end
     end
 
-    describe "dm with one other user" do
-      let(:usernames) { user1.username }
-      let(:direct_message_user_ids) { [current_user.id, user1.id] }
-
-      include_examples "creating dms"
-    end
-
     describe "dm with myself" do
       let(:usernames) { [current_user.username] }
       let(:direct_message_user_ids) { [current_user.id] }
 
-      include_examples "creating dms"
+      it "creates a new dm channel with username(s) provided" do
+        expect {
+          post "/chat/api/direct-message-channels.json", params: { target_usernames: [usernames] }
+        }.to change { Chat::DirectMessage.count }.by(1)
+        expect(Chat::DirectMessage.last.direct_message_users.map(&:user_id)).to match_array(
+          direct_message_user_ids,
+        )
+      end
+
+      it "returns existing dm channel if one exists for username(s)" do
+        create_dm_channel(direct_message_user_ids)
+
+        expect {
+          post "/chat/api/direct-message-channels.json", params: { target_usernames: [usernames] }
+        }.not_to change { Chat::DirectMessage.count }
+      end
     end
 
     describe "dm with two other users" do
       let(:usernames) { [user1, user2, user3].map(&:username) }
       let(:direct_message_user_ids) { [current_user.id, user1.id, user2.id, user3.id] }
 
-      include_examples "creating dms"
+      it "creates a new dm channel with username(s) provided" do
+        expect {
+          post "/chat/api/direct-message-channels.json", params: { target_usernames: [usernames] }
+        }.to change { Chat::DirectMessage.count }.by(1)
+        expect(Chat::DirectMessage.last.direct_message_users.map(&:user_id)).to match_array(
+          direct_message_user_ids,
+        )
+      end
+
+      it "createsa new dm channel" do
+        create_dm_channel(direct_message_user_ids)
+
+        expect {
+          post "/chat/api/direct-message-channels.json", params: { target_usernames: [usernames] }
+        }.to change { Chat::DirectMessage.count }.by(1)
+      end
     end
 
     it "creates Chat::UserChatChannelMembership records" do

plugins/chat/spec/requests/chat_controller_spec.rb

@@ -611,6 +611,7 @@ RSpec.describe Chat::ChatController do
       expect(response.status).to eq(403)
 
       Chat::DirectMessageUser.create(user: user, direct_message: dm_channel.chatable)
+
       expect {
         post "/chat/drafts.json", params: { chat_channel_id: dm_channel.id, data: "{}" }
       }.to change { Chat::Draft.count }.by(1)