Customized impersonating fingerprints

[T-256]

Is your feature request related to a problem? Please describe.
Yes, I think for solving #169 we need python level fingerprint generator.

Describe the solution you'd like
Ability to create impersonation in python level and use it in requests.

Describe alternatives you've considered
python-tls-client example

[yifeikong]

We need to get a list of customizable fields.

For TLS, there are too many, I have not bothered to collect them implementation is on the way.

For http2, we are almost there, only one part is missing everything is there.

All the options are listed here: https://github.com/yifeikong/curl-impersonate#libcurl-impersonate

We also need to implement a python class like ImpersonateSpec to specify the detailed instructions.

[yifeikong]

The first step is to be able to impersonate Firefox with BoringSSL.

• The cipher list option does not work as expected, TLS 1.3 suites always go as the first ones. Added in yifeikong/curl-impersonate@8997c93
• The extension order can not be changed. Tracked in Add an option to customized extension order curl-impersonate#24
• Add option for disabling GREASE. Tracked in Add an option to disable BoringSSL's GREASE behavior curl-impersonate#27
• Some extensions are missing, while some others should be disabled. Enable/disable tls extensions by given option string curl-impersonate#28
  • Disable signed_certificate_timestamp.(Can be easily turned off)
  • Disable application_settings.(Can be easily turned off)
  • Enable record_size_limit, which is not implemented by OpenSSL/BoringSSL, which means we have to do it ourselves. Tracked in Add fake record_size_limit option curl-impersonate#25
  • Enable delegated_credentials. BoringSSL only implemented the server side code, and it's using a different number for this extension. Since OpenSSL has not implemented it, it's unlikely that servers support this extension. We also need to implement this, but only fake the presense of it. It seems that only NSS supports these 2 extensions, utls fakes them anyway, we should do that too. Tracked in Add fake delegated credentials curl-impersonate#26

These issues need to be resolved at boringssl level.

• http2 stream priorities can not be customized. Added in yifeikong/curl-impersonate@1d9d7a7

This issue can be fixed at curl level.

After the above issues are fixed, we need to

• Export the struct impersonate_opts to Python via cffi.
• Create corresponding Python class.
• Add a parser to convert other easily accessible formats(e.g. browserleaks/peet.ws) to our internal format.