fix(secret): enforce basic auth credentials

This patch remove generation of a random string for the username and password of
the basic auth credentials.

The problem with the random generated basic auth credentials is, that this leads
to a new shasum of the secret. GitOps tools like ArgoCD detects a drift trigger
a rolling update.

To avoid this must now the basic auth credentials be defined to enable
prometheus metrics.

unittests/services/service.yaml

@@ -78,35 +78,35 @@ tests:
     service.internalTrafficPolicy: ""
   asserts:
   - failedTemplate:
-    errorMessage: No internal traffic policy defined!
+      errorMessage: No internal traffic policy defined!
 
 - it: Require port.
   set:
     service.port: ""
   asserts:
   - failedTemplate:
-    errorMessage: No service port defined!
+      errorMessage: No service port defined!
 
 - it: Require scheme.
   set:
     service.scheme: ""
   asserts:
   - failedTemplate:
-    errorMessage: No service scheme defined!
+      errorMessage: The scheme of the serviceMonitor is not defined!
 
 - it: Require sessionAffinity.
   set:
     service.sessionAffinity: ""
   asserts:
   - failedTemplate:
-    errorMessage: No session affinity defined!
+      errorMessage: No session affinity defined!
 
 - it: Require service type.
   set:
     service.type: ""
   asserts:
   - failedTemplate:
-    errorMessage: No service type defined!
+      errorMessage: No service type defined!
 
 - it: Render service with custom annotations and labels.
   set: