Add SessionAffinity to PGBouncer Service

[Pluggi]

Checklist:

• [x] Have you added an explanation of what your changes do and why you'd like them to be included?
• [x] Have you updated or added documentation for the change, as applicable?
• [x] Have you tested your changes on all related environments with successful results, as applicable?
  • [ ] Have you added automated tests?

Type of Changes:

• [x] New feature
• [ ] Bug fix
• [ ] Documentation
• [ ] Testing enhancement
• [ ] Other

What is the current behavior (link to any open issues here)?

N/A

What is the new behavior (if this is a feature change)?

• It just adds a parameter to the PostgresCluster CRD so that we can set the sessionAffinity.

Other Information: