Fix: allow repo job to support updates via PUT and blob store support

Currently, if you POST an existing/duplicate repo via Nexus 3.38.x API it breaks Nexus completely and requires a restart of the pod. The changes in the MR allow for an API GET to check if the repo already exists, and if so, performs a PUT instead of a POST. This will also allow for config updates to a repo.

Also, since Iron Bank uses s3 blob storage for their repos created via this chart, we've added a new section for creating a blob store via the chart in the same GET/POST/PUT fashion as the repo updates included here.

MR: https://repo1.dso.mil/platform-one/big-bang/apps/developer-tools/nexus/-/merge_requests/52