Use _human_readable for Runner's registration API

lib/api/runner.rb

@@ -14,10 +14,10 @@ module API
         optional :locked, type: Boolean, desc: 'Should Runner be locked for current project'
         optional :run_untagged, type: Boolean, desc: 'Should Runner handle untagged jobs'
         optional :tag_list, type: Array[String], desc: %q(List of Runner's tags)
-        optional :maximum_job_timeout, type: Integer, desc: 'Maximum timeout set when this Runner will handle the job'
+        optional :maximum_job_timeout_human_readable, type: String, desc: 'Maximum timeout set when this Runner will handle the job'
       end
       post '/' do
-        attributes = attributes_for_keys([:description, :locked, :run_untagged, :tag_list, :maximum_job_timeout])
+        attributes = attributes_for_keys([:description, :locked, :run_untagged, :tag_list, :maximum_job_timeout_human_readable])
           .merge(get_runner_details_from_request)
 
         runner =

spec/requests/api/runner_spec.rb

@@ -112,10 +112,20 @@ describe API::Runner do
       context 'when maximum job timeout is specified' do
         it 'creates runner' do
           post api('/runners'), token: registration_token,
-                                maximum_job_timeout: 7200
+                                maximum_job_timeout_human_readable: '2h 30m'
 
           expect(response).to have_gitlab_http_status 201
-          expect(Ci::Runner.first.maximum_job_timeout).to eq(7200)
+          expect(Ci::Runner.first.maximum_job_timeout).to eq(9000)
+        end
+
+        context 'when maximum job timeout is empty' do
+          it 'creates runner' do
+            post api('/runners'), token: registration_token,
+                                  maximum_job_timeout_human_readable: ''
+
+            expect(response).to have_gitlab_http_status 201
+            expect(Ci::Runner.first.maximum_job_timeout).to be_nil
+          end
         end
       end