refactor: change start behavior on missing credentials

[t1agob]

Description

This PR changes the start behaviour for the plugin by logging the error but still allowing the plugin to start. This change allows us to match what other Backstage plugins do.

Issue number: #26

Type of change

• [ ] New feature (non-breaking change which adds functionality)
• [x] Fix (non-breaking change which fixes an issue)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• [x] I have performed a self-review of this change
• [x] Changes have been tested
• [ ] Changes are documented
• [x] Changes generate no new warnings
• [x] PR title follows conventional commit semantics

If this is a breaking change 👇

• [ ] I have documented the migration process
• [ ] I have implemented necessary warnings (if it can live side by side)

Acknowledgement

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