Julien/config indexer 2

[julienrbrt]

Description

Updates #22218

cc @aaronc @cool-develope

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Author Checklist

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I have...

• included the correct type prefix in the PR title, you can find examples of the prefixes below:
• confirmed ! in the type prefix if API or client breaking change
• targeted the correct branch (see PR Targeting)
• provided a link to the relevant issue or specification
• reviewed "Files changed" and left comments if necessary
• included the necessary unit and integration tests
• added a changelog entry to CHANGELOG.md
• updated the relevant documentation or specification, including comments for documenting Go code
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I have...

• confirmed the correct type prefix in the PR title
• confirmed all author checklist items have been addressed
• reviewed state machine logic, API design and naming, documentation is accurate, tests and test coverage

[github-actions]

@julienrbrt your pull request is missing a changelog!

[aaronc]

Can we should some example postgres config here?

[julienrbrt]

we cannot really, best would be to prewrite the postgres one instead and register it (otherwise it complains indexer type doesn't exist)