FEATURE: Allow admins to remove users from chat DMs (#31366)

This feature allows admins to remove users from channels.

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

@@ -2,14 +2,16 @@
 
 RSpec.describe Chat::Api::ChannelsMembershipsController do
   fab!(:current_user) { Fabricate(:user) }
+  fab!(:other_user) { Fabricate(:user) }
   fab!(:channel_1) do
-    Fabricate(:direct_message_channel, group: true, users: [current_user, Fabricate(:user)])
+    Fabricate(:direct_message_channel, group: true, users: [current_user, other_user])
   end
 
   before do
     SiteSetting.chat_enabled = true
     SiteSetting.chat_allowed_groups = Group::AUTO_GROUPS[:everyone]
     channel_1.add(current_user)
+    channel_1.add(other_user)
     sign_in(current_user)
   end
 
@@ -52,4 +54,42 @@ RSpec.describe Chat::Api::ChannelsMembershipsController do
       end
     end
   end
+
+  describe "#destroy" do
+    context "when acting user is an admin" do
+      let(:current_user) { Fabricate(:admin) }
+
+      describe "success" do
+        it "works" do
+          delete "/chat/api/channels/#{channel_1.id}/memberships/#{other_user.id}"
+
+          expect(response.status).to eq(200)
+        end
+      end
+
+      context "when channel is not found" do
+        it "returns a 404" do
+          delete "/chat/api/channels/-999/memberships/#{other_user.id}"
+
+          expect(response.status).to eq(404)
+        end
+      end
+
+      context "when target user is not found" do
+        it "returns a 404" do
+          delete "/chat/api/channels/#{channel_1.id}/memberships/31337"
+
+          expect(response.status).to eq(404)
+        end
+      end
+    end
+
+    context "when acting user is not an admin" do
+      it "returns a 403" do
+        delete "/chat/api/channels/#{channel_1.id}/memberships/#{other_user.id}"
+
+        expect(response.status).to eq(403)
+      end
+    end
+  end
 end