[dev] Add customize fingerprint

[LuckyPigeon]

Description

request_fingerprint is deprecated in Scrapy, but new fingerprint function requires a lot of changes of our code. Thus we need a customize fingerprint implementation for our own.

Unittests are also implemented, there are three new unittests

• test_request_seen with
  • same_request
  • diff_method
  • diff_url

Fixes #272

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• [x] pytest

Test Configuration:

• OS version: Windows10 & WSL

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] Any dependent changes have been merged and published in downstream modules

[LuckyPigeon]

@rmax Do we need a unit test for this implementation? This function might not be called by others, right?

[rmax]

My suggestion would be to refactor the fingerprint method logic into a function and unit test the behavior of this function:

• two calls to the same request returns the same fingerprint,
• the fingerprint of two different requests are different (I.e.: same url but different http method)

[LuckyPigeon]

Sounds great.

[LuckyPigeon]

@rmax done!