Process request headers

[elacuesta]

Partially address #36.

Allow to override the processing of request headers via the PLAYWRIGHT_PROCESS_REQUEST_HEADERS setting. For instance, set PLAYWRIGHT_PROCESS_REQUEST_HEADERS=scrapy_playwright.headers.use_playwright_headers to use Playwright headers and ignore the ones coming from Scrapy.

Names are subject to change, I'm open to suggestions.

Tasks:

• Code
• Tests
• Docs

[codecov]

Codecov Report

Merging #38 (16ac2a2) into master (2ca67f3) will not change coverage.
The diff coverage is 100.00%.

❗ Current head 16ac2a2 differs from pull request most recent head 42a1280. Consider uploading reports for the commit 42a1280 to get more accurate results

@@            Coverage Diff            @@
##            master       #38   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            3         4    +1     
  Lines          185       203   +18     
=========================================
+ Hits           185       203   +18     

Impacted Files	Coverage Δ
scrapy_playwright/handler.py	100.00% <100.00%> (ø)
scrapy_playwright/headers.py	100.00% <100.00%> (ø)

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[Gallaecio]

Looks good to me, pending the documentation.

[Gallaecio]

Shame, this could be a 1-liner in Scrapy 2.4+ 🙁

(technically also here, but I’m guessing you don’t want to have load_object parse a string in the default scenario)

[elacuesta]

Indeed, I'd like to avoid any (admittedly small) overhead if we already have the object.

This is a nice catch, I was planning on documenting the setting as accepting either paths or functions directly, but didn't remember that was only valid on Scrapy 2.4+. I'll be sure to mention that when I write the docs, thanks!