Simple cache

[sjvrijn]

Adding a simple LRU cache to the api.others.toggl() function that dispatches the API calls.
Can be disabled using configuration option cache_requests, and size can be set with cache_size.
Cache is cleared in all functions that dispatch a PUT, POST or DELETE API call.

[sjvrijn]

Relevant to #86, but as mentioned there: this PR is not intended to close it yet.

[AuHau]

Generally looks good! There needs to be a better way how to support turning on/off the caching as mentioned in my comment.

Also, I am a bit worried about one thing. If by any chance API responds with some error message, this response then will be cached even though it should not be and should be retried later on. Hence we should cache only 200 responses and to be even more concrete we should cache only GET requests because otherwise, we might get problems with any modifications requests being ignored.
Unfortunately, it seems that the lru_cache has very limited support for such operations. So I am bit afraid that we should look into some more advanced caching options. Do you know about any?

[AuHau]

Hmm I am afraid we can't do this. Config.factory() will always give you the default ~/.togglrc configuration, which might not be desired for people who build their own Config instance that they pass to the API Wrappers.

[AuHau]

Hmm we could wrap instead of toggl() the _toggl_request() function and then in toggl() decide based on the passed config if used the cached version or instead non-cached version using the ability to bypass the cache using _toggl_request. __wrapped__() attribute that lru_cache expose. This then can be also used to ignore cache for POST/DELETE/PUT requests.

But still, it leaves us with the problem of caching error response...

[AuHau]

Also, it will be needed to write test coverage for this to make sure that we are not missing anything.

[sjvrijn]

Thanks for the feedback!
The _toggl_request() cannot be cached using the default lru_cache, as it takes a non-hashable input. Also, you raise a good point for not wanting to cache any non-200 responses, making it difficult to use the lru_cache anyway.
I'll have a look at replacing it with a more custom caching solution. After all, Python's lru_cache is also simply a dictionary. Would you be okay with integrating the caching in e.g. the toggl() function? I wouldn't know how to integrate a different run-time config object into a decorator-style wrapper.

[AuHau]

Hey,
since there is no progress on this PR, I am gonna close it for now. If you decide to come back to it, feel free to reopen.