docs: Add sample-configuration for TLS client options

[srebhan]

• Updated associated README.md.
• Wrote appropriate unit tests.
• Pull request title or commits are in conventional commit format

Add a sample-configuration for the TLS client-config.

[powersj]

overall love having this so we keep things in sync! just one question about naming that was throwing me off while reviewing this.

[srebhan]

After some more thoughts this approach has several drawbacks:

1. With plugins ending with a map definition in TOML e.g. [inpus.modbus.workarounds] this approach will not be possible and will generate malformed (and/or confusing) TOML files.
2. The sample.conf files do no longer match the output of the SampleConfig function call.
3. Inserting into a config structure is very limited as you can only add stuff at the beginning or end.
4. There is no way to comment/uncomment an embedded config in a good way.

Given all those limitation (especially 1 and 2) I'm closing this PR as we need to come up with something more flexible.

[Hipska]

1 could be solved by not including it for those kind of plugins, but I agree to close and find a better solution.

Maybe let sample.conf be a golang template where you include the tls.conf?

[srebhan]

Maybe let sample.conf be a golang template where you include the tls.conf?

@Hipska that would be one way. In any way we should generate a sample.conf that is the rendered result and check that in to the repo. So this calls for another "generator" running with make docs...

[Hipska]

I don't see the need for that, why would that rendered sample.conf need to be checked in the repo? (It only needs to be rendered in the readme, but that is currently already the case.)

In other words, why is N°2 a problem?

[Hipska]

I do like the tls client.conf sample, that should be added to the repo anyway.

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[powersj]

@srebhan close this PR in favor of #13348 ?

[srebhan]

Fine with me.