indent JSON files generated by fetch-deps command

[slimreaper35]

within user request, we write out json files (bom.json, .build-config.json) by model_dump_json()method, but with no indentation so the output is a huge one-line file

unlike generating data in integration tests: https://github.com/containerbuildsystem/cachi2/blob/main/tests/integration/utils.py#L228

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• [x] Commit messages are descriptive enough
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[eskultety]

Yes, I ran into this with https://github.com/containerbuildsystem/cachi2/pull/500/, it's painful.

[slimreaper35]

just rebased