Pyramid-oauthlib-lowlevel

* drop Python3.6, as SqlAlchemy2.0 is required for tests
* Additional typing
* `request.access_token` is now a private `request.access_token_object`,
which is this package (and integrators') datastore backed object to
more properly isolate it from the various oAuthlib token instances.
* Removed deprecated functions:
* oauth1.validator.OAuth1RequestValidator_Hooks.create_access_token_existing
* oauth1.validator.OAuth1RequestValidator.create_access_token_existing
* tests.oauth1_utils.CustomValidator_Hooks.create_access_token_existing
* require typing_extensions as `Literal` is not in Python3.7
* Changed:
OAuth2RequestValidator_Hooks.bearer_token_setter
`token` -> `token_dict`

OAuth2RequestValidator_Hooks.bearer_token_setter
`access_token` -> `access_token_str`
`refresh_token` -> `refresh_token_str`

OAuth2RequestValidator_Hooks.token_getter
`access_token` -> `access_token_str`
`refresh_token` -> `refresh_token_str`

OAuth2RequestValidator.validate_bearer_token
`token` -> `token_str`

OAuth2RequestValidator.validate_bearer_token
`refresh_token` -> `refresh_token_str`

OAuth1RequestValidator_Hooks.access_token_getter
`token` -> `token_str`

OAuth1RequestValidator_Hooks.access_token_setter
`token` -> `token_dict`

OAuth1RequestValidator_Hooks.request_token_getter
`token` -> `token_str`

OAuth1RequestValidator_Hooks.request_token_setter
`token` -> `token_dict`

OAuth1RequestValidator_Hooks.request_token_invalidator
`request_token` -> `token_str`

OAuth1RequestValidator_Hooks.nonce_getter
`request` now 4th arg
`access_token` -> `access_token_str`
`refresh_token` -> `refresh_token_str`

OAuth1RequestValidator_Hooks.nonce_setter
`request` now 4th arg
`access_token` -> `access_token_str`
`refresh_token` -> `refresh_token_str`

OAuth1RequestValidator_Hooks.verifier_getter
`verifier` -> `verifier_str`
`token` -> `token_str`

OAuth1RequestValidator_Hooks.verifier_setter
`verifier` -> `verifier_str`
`token` -> `token_str`

OAuth1RequestValidator._get_RequestTokenObject
`token` -> `token_str`

OAuth1RequestValidator.get_request_token_secret
`token` -> `token_str`

OAuth1RequestValidator.get_access_token_secret
`token` -> `token_str`

OAuth1RequestValidator.get_realms
`token` -> `token_str`

OAuth1RequestValidator.get_redirect_uri
`token` -> `token_str`

OAuth1RequestValidator.validate_request_token
`token` -> `token_str`

OAuth1RequestValidator.validate_access_token
`token` -> `token_str`

OAuth1RequestValidator.validate_timestamp_and_nonce
`request` now 4th arg

OAuth1RequestValidator.validate_realms
`token` -> `token_str`

OAuth1RequestValidator.validate_verifier
`token` -> `token_str`
`verifier` -> `verifier_str`

OAuth1RequestValidator.verify_request_token
`token` -> `token_str`

OAuth1RequestValidator.verify_realms
`token` -> `token_str`

OAuth1RequestValidator.save_access_token
`token` -> `token_dict`

OAuth1RequestValidator.save_request_token
`token` -> `token_dict`

OAuth1RequestValidator.save_verifier
`token` -> `token_str`
`verifier` -> `verifier_str`

* drop py2.7,py35
* initial mypy support

* fixed try/except black that did not properly catch an exception scenario
* rely on six instead of copying some functions from other projects
* cleanup imports
* cleanup rst formatting

* packaging
* removed pyramid_compat
* should work on pyramid1.x and 2.x

* black
* upgraded black; 20.8b1
* integrated with pre-commit
* packaging

small changes to the api client regarding content decoding