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/secrets/basicAuth.yaml

@@ -13,9 +13,29 @@ tests:
   - hasDocuments:
       count: 0
 
+- it: Throw error for missing basic auth password
+  set:
+    prometheus.metrics.enabled: true
+    # prometheus.metrics.secret.new.basicAuthPassword: "my-password"
+    prometheus.metrics.secret.new.basicAuthUsername: "my-username"
+  asserts:
+    - failedTemplate:
+        errorMessage: "Password for basic auth is required!"
+
+- it: Throw error for missing basic auth username
+  set:
+    prometheus.metrics.enabled: true
+    prometheus.metrics.secret.new.basicAuthPassword: "my-password"
+    # prometheus.metrics.secret.new.basicAuthUsername: "my-username"
+  asserts:
+    - failedTemplate:
+        errorMessage: "Username for basic auth is required!"
+
 - it: Rendering secret with default values.
   set:
     prometheus.metrics.enabled: true
+    prometheus.metrics.secret.new.basicAuthPassword: "my-password"
+    prometheus.metrics.secret.new.basicAuthUsername: "my-username"
   asserts:
   - hasDocuments:
       count: 1
@@ -51,13 +71,13 @@ tests:
   asserts:
   - hasDocuments:
       count: 1
-  - exists:
+  - isSubset:
       path: metadata.annotations
-      value:
+      content:
         foo: bar
-  - exists:
+  - isSubset:
       path: metadata.labels
-      value:
+      content:
         bar: foo
   - equal:
       path: metadata.name