Injector stats

[proway2]

Fixes #158

• For every internal dependency that's being injected there will be a record in Scrapy stats:

poet/injector/tests.test_injection.PricePO 15

• Other places in the injector, where stats are produced, have updated prefix poet/*
• pytest-twisted is added to requirements-dev.txt otherwise it's impossible to set up the local env (tox works fine in any case)

[codecov]

Codecov Report

Merging #161 (4c30856) into master (50c4578) will increase coverage by 0.05%.
The diff coverage is 100.00%.

❗ Current head 4c30856 differs from pull request most recent head 0ab0e40. Consider uploading reports for the commit 0ab0e40 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #161      +/-   ##
==========================================
+ Coverage   85.62%   85.67%   +0.05%     
==========================================
  Files          14       14              
  Lines         800      803       +3     
==========================================
+ Hits          685      688       +3     
  Misses        115      115              

Files Changed	Coverage Δ
scrapy_poet/injection.py	98.49% <100.00%> (+0.02%)	⬆️

[Gallaecio]

Looks good to me.

I do wonder if we should mention in the Stats page of the documentation the stats that are logged beyond those that are created using web-poet stats. Or maybe just mention the kind of stuff that’s logged, without going into detail.

[proway2]

@Gallaecio I'll add a short note to docs, without details though.

[proway2]

@Gallaecio when this could potentially be merged and released?

[kmike]

Thanks @proway2!