Provide more examples / detailed docs on custom request header override per spider

[DaniruKun]

I have a situation where I need to supply a custom consent cookie to a specific spider. While it is described how to do it for the middleware, it is not very clear still how to pass e.g. custom headers to the init/1 callback of Crawly.Spider.

Even a small example or such will help and can help with writing a good example in docs, thanks!

[darkslategrey]

Why not use start_requests: ?

crawly/test/manager_test.exs

Line 165 in c02e408

def init() do

[Ziinc]

https://hexdocs.pm/crawly/basic_concepts.html#behaviour-functions

[Ziinc]

• add in examples
  • add to https://hexdocs.pm/crawly/basic_concepts.html#behaviour-functions, link to callback docs
  • add to https://hexdocs.pm/crawly/Crawly.Spider.html#c:init/1 , main doc reference.