Add -modules support

[Rustin170506]

close #367

Try to add -modules support. Most code from mimir.

[Rustin170506]

@cyriltovena Could you please take a look? Thanks! 💚 💙 💜 💛 ❤️

[simonswine]

Thanks for working on this, this is super useful to have.

I only have one request, could add the existence of that flag to the -help output? Currently it is not mentioned at all. You could modify -target or also register a separate flag there (or maybe even both)

[Rustin170506]

I only have one request, could add the existence of that flag to the -help output?

Of course. Also, I noticed that phlare's current help info has some problems. like it uses the wrong name.

➜  phlare git:(main) ✗ ./main --help            
Usage of config-file-loader:
  -auth.multitenancy-enabled
        When set to true, incoming HTTP requests must specify tenant ID in HTTP X-Scope-OrgId header. When set to false, tenant ID anonymous is used instead.
  -client.tenant-id string
        Tenant ID to use when pushing profiles to Phlare (default: anonymous). (default "anonymous")
  -client.url value
        URL of log server.
  -config.expand-env
        Expands ${var} in config according to the values of the environment variables.

I'll fix it together.

[simonswine]

@simonswine Friendly ping~ Thank you!

@hi-rustin I am really sorry that it took so long. Keep pinging and eventually I will get to it 🙂.

I would prefer we change the structure of cmd/phlare.main to be more aligned with cmd/mimir.main, let me know if you don't think that is a good idea.

[Rustin170506]

Self check

[Rustin170506]

@simonswine
Thanks for reviewing! 💚 💙 💜 💛 ❤️

It is ready for another review.

Also, I think we still have some work to do.

1. add a test for the CLI help text, then we can notice what has changed after every PR
2. add a test mode to test some abnormal scenarios, like getting an unknown args. Now we cannot test it because we called os.Exit.

I can do it in my following PRs. Because it's off this topic.

[simonswine]

Yes fully agree with solving those problems are off-topic to this PR, it is gotten large enough already.

Thank you so much for going through the review rounds. LGTM

[Rustin170506]

Thanks for your review! 💚 💙 💜 💛 ❤️