FEATURE: Add page for all group membership requests. (#6909)

db/migrate/20190117191606_create_group_requests.rb

@@ -0,0 +1,14 @@
+class CreateGroupRequests < ActiveRecord::Migration[5.2]
+  def change
+    create_table :group_requests do |t|
+      t.integer :group_id
+      t.integer :user_id
+      t.text :reason
+
+      t.timestamps
+    end
+
+    add_index :group_requests, :group_id
+    add_index :group_requests, :user_id
+  end
+end