Remove unused UsersController#suggests

https://gitlab.com/gitlab-org/gitlab/-/merge_requests/57563 replaced the
functionality of namespace suggestion checking with an API endpoint.

https://gitlab.com/gitlab-org/gitlab/-/issues/327807

app/controllers/users_controller.rb

@@ -20,7 +20,7 @@ class UsersController < ApplicationController
 
   skip_before_action :authenticate_user!
   prepend_before_action(only: [:show]) { authenticate_sessionless_user!(:rss) }
-  before_action :user, except: [:exists, :suggests, :ssh_keys]
+  before_action :user, except: [:exists, :ssh_keys]
   before_action :authorize_read_user_profile!,
                 only: [:calendar, :calendar_activities, :groups, :projects, :contributed, :starred, :snippets, :followers, :following]
 
@@ -153,14 +153,6 @@ class UsersController < ApplicationController
     render json: { exists: !!Namespace.find_by_path_or_name(params[:username]) }
   end
 
-  def suggests
-    namespace_path = params[:username]
-    exists = !!Namespace.find_by_path_or_name(namespace_path)
-    suggestions = exists ? [Namespace.clean_path(namespace_path)] : []
-
-    render json: { exists: exists, suggests: suggestions }
-  end
-
   def follow
     current_user.follow(user)
 

config/routes/user.rb

@@ -49,7 +49,6 @@ scope(constraints: { username: Gitlab::PathRegex.root_namespace_route_regex }) d
     get :followers
     get :following
     get :exists
-    get :suggests
     get :activity
     post :follow
     post :unfollow

spec/requests/users_controller_spec.rb

@@ -675,48 +675,6 @@ RSpec.describe UsersController do
     end
   end
 
-  describe 'GET #suggests' do
-    context 'when user exists' do
-      it 'returns JSON indicating the user exists and a suggestion' do
-        get user_suggests_url user.username
-
-        expected_json = { exists: true, suggests: ["#{user.username}1"] }.to_json
-        expect(response.body).to eq(expected_json)
-      end
-
-      context 'when the casing is different' do
-        let(:user) { create(:user, username: 'CamelCaseUser') }
-
-        it 'returns JSON indicating the user exists and a suggestion' do
-          get user_suggests_url user.username.downcase
-
-          expected_json = { exists: true, suggests: ["#{user.username.downcase}1"] }.to_json
-          expect(response.body).to eq(expected_json)
-        end
-      end
-    end
-
-    context 'when the user does not exist' do
-      it 'returns JSON indicating the user does not exist' do
-        get user_suggests_url 'foo'
-
-        expected_json = { exists: false, suggests: [] }.to_json
-        expect(response.body).to eq(expected_json)
-      end
-
-      context 'when a user changed their username' do
-        let(:redirect_route) { user.namespace.redirect_routes.create!(path: 'old-username') }
-
-        it 'returns JSON indicating a user by that username does not exist' do
-          get user_suggests_url 'old-username'
-
-          expected_json = { exists: false, suggests: [] }.to_json
-          expect(response.body).to eq(expected_json)
-        end
-      end
-    end
-  end
-
   describe '#ensure_canonical_path' do
     before do
       sign_in(user)