Move runner pagination support to controllers

Having mandatory pagination does not make sense if we reuse this class
for GraphQL queries

app/controllers/admin/runners_controller.rb

@@ -7,9 +7,11 @@ class Admin::RunnersController < Admin::ApplicationController
 
   feature_category :continuous_integration
 
+  NUMBER_OF_RUNNERS_PER_PAGE = 30
+
   def index
     finder = Ci::RunnersFinder.new(current_user: current_user, params: params)
-    @runners = finder.execute
+    @runners = finder.execute.page(params[:page]).per(NUMBER_OF_RUNNERS_PER_PAGE)
     @active_runners_count = Ci::Runner.online.count
     @sort = finder.sort_key
   end

app/finders/ci/runners_finder.rb

@@ -4,8 +4,6 @@ module Ci
   class RunnersFinder < UnionFinder
     include Gitlab::Allowable
 
-    NUMBER_OF_RUNNERS_PER_PAGE = 30
-
     def initialize(current_user:, group: nil, params:)
       @params = params
       @group = group
@@ -18,7 +16,6 @@ module Ci
       filter_by_runner_type!
       filter_by_tag_list!
       sort!
-      paginate!
 
       @runners.with_tags
 
@@ -77,10 +74,6 @@ module Ci
       @runners = @runners.order_by(sort_key)
     end
 
-    def paginate!
-      @runners = @runners.page(@params[:page]).per(NUMBER_OF_RUNNERS_PER_PAGE)
-    end
-
     def filter_by!(scope_name, available_scopes)
       scope = @params[scope_name]
 

spec/finders/ci/runners_finder_spec.rb

@@ -72,17 +72,6 @@ RSpec.describe Ci::RunnersFinder do
         end
       end
 
-      context 'paginate' do
-        it 'returns the runners for the specified page' do
-          stub_const('Ci::RunnersFinder::NUMBER_OF_RUNNERS_PER_PAGE', 1)
-          runner1 = create :ci_runner, created_at: '2018-07-12 07:00'
-          runner2 = create :ci_runner, created_at: '2018-07-12 08:00'
-
-          expect(described_class.new(current_user: admin, params: { page: 1 }).execute).to eq [runner2]
-          expect(described_class.new(current_user: admin, params: { page: 2 }).execute).to eq [runner1]
-        end
-      end
-
       context 'non admin user' do
         it 'returns no runners' do
           user = create :user
@@ -172,38 +161,6 @@ RSpec.describe Ci::RunnersFinder do
         end
       end
 
-      context 'paginate' do
-        using RSpec::Parameterized::TableSyntax
-
-        let(:runners) do
-          [[runner_project_7, runner_project_6, runner_project_5],
-           [runner_project_4, runner_project_3, runner_project_2],
-           [runner_project_1, runner_sub_group_4, runner_sub_group_3],
-           [runner_sub_group_2, runner_sub_group_1, runner_group]]
-        end
-
-        where(:page, :index) do
-          1 | 0
-          2 | 1
-          3 | 2
-          4 | 3
-        end
-
-        before do
-          stub_const('Ci::RunnersFinder::NUMBER_OF_RUNNERS_PER_PAGE', 3)
-
-          group.add_owner(user)
-        end
-
-        with_them do
-          let(:params) { { page: page } }
-
-          it 'returns the runners for the specified page' do
-            expect(subject).to eq(runners[index])
-          end
-        end
-      end
-
       context 'filter by search term' do
         let(:params) { { search: 'runner_project_search' } }