Pass .annotaterb.yml through ERB

[fxn]

Hi!

This PR proposes passing .annotaterb.yml through ERB, as Rails does with config/database.yml or fixtures, for instance.

Real use case is the ability to compute model_dir dynamically. As you know, in annotate the configuration can be expressed in Ruby, and therefore it can be as dynamic as you need to. But if you migrate to annotaterb, that is lost.

I wrote this patch on behalf of a client of mine (Gusto), whose main application has more than two hundred model dirs. They are now hard-coded in .annotaterb.yml, but you need to maintain that list, verify consistency in CI, etc. On the other hand, if you could compute the list in the config file itself, you could forget about it (as it was the case with annotate).

I have created a test suite for load_config, and documentation is also updated (README and migration guide). The variable yaml_code is named after the parameter in the signature of the called method.

The CHANGELOG seems more ad-hoc, maybe you prefer to modify this one? Please just tell me if you'd like me to do it anyway :).

[drwl]

Hi @fxn thanks for submitting this. Happy to help get this merged this in, seems like there might be an unrelated 2.7 error and then just needs linting via standard.

[drwl]

I merged in a PR that drops Ruby 2.7 support, so if you rebase or merge latest development, it'll "fix" the unit test that is failing in 2.7

[fxn]

Thanks @drwl! Branch updated and standard is green now.

[drwl]

Just fyi, I released 4.16.0 and it should contain this change.

[fxn]

@drwl that's awesome, thank you!