Introduce ZYTE_API_MAX_REQUESTS

[BurnzZ]

An attempt on #111 to gather feedback.

This has minimal changes that only addresses the limits on ZAPI Requests.

In the future, we also might want to impose other limits like the following which may affect the implementation:

• item count
• per data type
• per page type
• etc

TODO

• README

[codecov]

Codecov Report

Merging #114 (d0d4f8f) into main (23762b6) will increase coverage by 9.00%.
Report is 1 commits behind head on main.
The diff coverage is 100.00%.

❗ Current head d0d4f8f differs from pull request most recent head 2820d56. Consider uploading reports for the commit 2820d56 to get more accurate results

@@            Coverage Diff             @@
##             main     #114      +/-   ##
==========================================
+ Coverage   89.48%   98.49%   +9.00%     
==========================================
  Files           9        9              
  Lines         647      666      +19     
==========================================
+ Hits          579      656      +77     
+ Misses         68       10      -58     

Files Changed	Coverage Δ
scrapy_zyte_api/_downloader_middleware.py	100.00% <100.00%> (ø)
scrapy_zyte_api/_params.py	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes

[wRAR]

As, I think, this code will be executed several times, I wonder how will it look in the log, hopefully not too ugly.

[BurnzZ]

There should just be a few of them since the spider is immediately closed.

[Gallaecio]

As long as the message reads “this request is skipped because the max has been reached” rather than just “the max has been reached”, I think it is OK for this to appear several times.

[BurnzZ]

Message updated in 660cdb2

[wRAR]

I think the approach is fine, though I haven't thought about the download_req_count calculation.

[BurnzZ]

Hey folks, I've unmarked this one as draft.

I think we can think about other things to set as max like item count, per data type, per page type, etc in another future PR.

[kmike]

Thanks @BurnzZ!