[AAE-622] No implicit returns (#5157)

* enable noImplicitReturns rule

* type fixes

* fix return types

* fix return value

* fix tests

* fix visibility service

* update tests

* add missing types

* fix test

lib/process-services/src/lib/process-list/components/process-instance-header.component.ts

@@ -120,6 +120,7 @@ export class ProcessInstanceHeaderComponent implements OnChanges {
         if (this.processInstance) {
             return this.isRunning() ? 'Running' : 'Completed';
         }
+        return 'Unknown';
     }
 
     getStartedByFullName(): string {