Jl/edit image secrets paths

[jordlay]

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Fixed regex to be more general, small refactor of code to do so. Tested with Olya's code examples and SAS example.

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Related command

az aosm nfd build --config-file cnf_input.json --definition-type cnf

General Guidelines

• Have you run azdev style <YOUR_EXT> locally? (pip install azdev required)
• Have you run python scripts/ci/test_index.py -q locally?

For new extensions:

• My extension description/summary conforms to the Extension Summary Guidelines.

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