Add pdb

[bryopsida]

What this PR does / why we need it:

Adds a optional PDB to make node drains/cordons safer

Which issue this PR fixes

• fixes #49

Special notes for your reviewer:

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.

• [x] Chart Version bumped
• [x] e2e tests pass
• [x] Variables are documented in the README.md

[willholley]

thanks for the PR @bryopsida. It seems that CI is failing, though I'm not entirely sure why - it passes locally for me so is perhaps a timing issue.

[bryopsida]

thanks for the PR @bryopsida. It seems that CI is failing, though I'm not entirely sure why - it passes locally for me so is perhaps a timing issue.

I tested out a white space only change here: https://github.com/bryopsida/couchdb-helm/actions/runs/4986433003 and that worked so it seems isolated to this branch.

When I have some more time I'll try and isolate what's going on.

[bryopsida]

@willholley looks like I was missing a null check on podDisruptionBudget, I was counting on the default value being present but looks like that's not the case in CI.

I tested it here https://github.com/bryopsida/couchdb-helm/actions/runs/5032284491 and here https://github.com/bryopsida/couchdb-helm/actions/runs/5032313655 and it worked.