Do not modify the Spec with SuperuserSecretName, only the dcConfig. A…

[burmanm]

…lso, do not mount any secrets to cassandra container

What this PR does:

• Do not modify the K8ssandraCluster object when superuserSecretName isn't set, instead set it at the dcConfig creation.
• Remove injected secret from the cassandra container as it isn't used by anything.

Which issue(s) this PR fixes:
Fixes #1235

Checklist

• Changes manually tested
• Automated Tests added/updated
• Documentation added/updated
• CHANGELOG.md updated (not required for documentation PRs)
• CLA Signed: DataStax CLA

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 57.44%. Comparing base (6ad0ed0) to head (04aa129).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1237      +/-   ##
==========================================
+ Coverage   57.30%   57.44%   +0.14%     
==========================================
  Files         103      103              
  Lines       10794    10783      -11     
==========================================
+ Hits         6185     6194       +9     
+ Misses       4069     4054      -15     
+ Partials      540      535       -5     

Files	Coverage Δ
pkg/secret/inject.go	76.19% <ø> (+3.46%)	⬆️
controllers/k8ssandra/dcconfigs.go	76.81% <50.00%> (+0.34%)	⬆️
controllers/k8ssandra/secrets.go	71.64% <83.33%> (+8.00%)	⬆️

... and 3 files with indirect coverage changes

[sonarqubecloud]

Quality Gate failed

Failed conditions
4.4% Duplication on New Code (required ≤ 3%)

See analysis details on SonarCloud