Allow to skip execution of FieldCoverageMonitor if no item is returned

[VladAlex98]

Closes #366

Added another setting called SPIDERMON_FIELD_COVERAGE_SKIP_IF_NO_ITEM for FieldCoverageMonitor:

• If this setting is enabled and we don't have any items scraped, it will not raise error anymore, it will send a message instead.

[rennerocha]

Hello @VladAlex98 ,
Thanks for your contribution. I added a suggestion so the logs returned for the user would looks nicer and more consistent with other monitor results logs that we have in other built-in monitors.
Also, do not forget to add unit tests for your change and update the documentation of FieldCoverageMonitor adding this new setting.

[rennerocha]

suggestion If we are skipping a test, in my opinion we should use the same pattern as we have in BaseStatMonitor (see code here).

Calling self.skipTest("No items returned") inside FieldCoverageMonitor.test_check_if_field_coverage_rules_are_met if the setting is set and there is no items returned (instead of just return inside FieldCoverageMonitor.run) will make the logs look nicer as:

2022-12-15 15:55:43 [quotes] INFO: [Spidermon] ------------------------------ MONITORS ------------------------------
2022-12-15 15:55:43 [quotes] INFO: [Spidermon] Field Coverage Monitor/test_check_if_field_coverage_rules_are_met... SKIPPED (No items returned)
2022-12-15 15:55:43 [quotes] INFO: [Spidermon] ----------------------------------------------------------------------

An alternative then would be:

def test_check_if_field_coverage_rules_are_met(self):
    skip_if_no_items = self.crawler.settings.get('SPIDERMON_FIELD_COVERAGE_SKIP_IF_NO_ITEM', False)
    items_scraped = self.data.stats.get('item_scraped_count', 0
    if skip_if_no_items and items_scraped == 0:
        self.skipTest("No items were scraped")

    # continue with existing code

[VladAlex98]

Hi @rennerocha, thanks for the code review. I updated the code, added docs and some tests. Please let me know if you need to add something else.

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.02 🎉

Comparison is base (558aace) 76.41% compared to head (a918c16) 76.44%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #372      +/-   ##
==========================================
+ Coverage   76.41%   76.44%   +0.02%     
==========================================
  Files          76       76              
  Lines        3193     3197       +4     
  Branches      378      379       +1     
==========================================
+ Hits         2440     2444       +4     
  Misses        683      683              
  Partials       70       70              

Impacted Files	Coverage Δ
spidermon/contrib/scrapy/monitors/monitors.py	97.89% <100.00%> (+0.04%)	⬆️

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[VMRuiz]

Hello @rennerocha , is this good now?

[curita]

Changes look good!

I mentioned a small suggestion, but otherwise, the functionality makes sense to me.

Requested changes were implemented