Move make_identifier function to collect.py

[Lotram]

in aggregate_issues, we have both the Issue object and the deserialized data, so we can compute the identifier without relying on a fragile iteration on list of key_lists Also add some more precise typing

[Lotram]

Turns out I had a types.py to avoid cyclic dependency issues. I changed two things:

• get_service is now defined in services/__init__.py, as it makes more sense than to define it in collect.py
• config/__init__.py now only import (and re-export) objects used in the public API. It used to import all files, creating cyclic dependencies much more "easily".

[ryneeverett]

Turns out I had a types.py to avoid cyclic dependency issues. I changed two things:

* `get_service` is now defined in `services/__init__.py`, as it makes more sense than to define it in `collect.py`

* `config/__init__.py` now only import (and re-export) objects used in the public API. It used to import all files, creating cyclic dependencies much more "easily".

It isn't clear to me that these changes are desirable. Could they be dropped now that the types are in collect.py?

[Lotram]

I'd keep the change on get_service. IMO, there is really no good reason to have it in collect.py. For now, config, as a modules, depends on collect.py, but it should not. If not in services/__init__.py, I think it should be somewhere in config/ (maybe validation.py ?), so that config does not depend on anything.

If we make sure of that (config not depending on anything), then I can revert the change on config/__init__.py, since we're sure that importing all config files can't be an issue for other modules.

[ryneeverett]

Keeping get_service in services/__init__.py and reverting the config/__init__.py changes makes sense to me. (Now that I look at get_service from a dependency perspective I see what you mean.)

[Lotram]

I moved get_service definition to avoid a dependency config --> services --> config.
Config now depends only on itself, no imports from other bugwarrior files.

And I removed changes on config/__init__.py