DDLS-379 add a read only user

[jamesrwarren]

Purpose

Add a read only DB user

Fixes DDLS-379

Approach

Full details here: https://opgtransform.atlassian.net/jira/software/c/projects/DDLS/boards/197?selectedIssue=DDLS-379

Learning

NA

Checklist

• I have performed a self-review of my own code
• I have updated documentation (Confluence/ADR/tech debt doc) where relevant
• I have added tests to prove my work
• The product team have approved these changes
• I have checked my work for potential security issues and refered to the OWASP top 10

Frontend

• I have run an in-browser accessibility test (e.g. WAVE, Lighthouse)
• There are no deprecated CSS classes noted in the profiler
• Translations are used and the profiler doesn't identify any missing
• Any links or buttons added are screen reader friendly and contextually complete
• If adding GA events, I have updated or checked the existing category or label values