Migrate documentation to Docusaurus

Remove Travis configuration

Co-authored-by: Nick Meves <nick.meves@greenhouse.io>

* Implement azure token refresh

Based on original PR https://github.com/oauth2-proxy/oauth2-proxy/pull/278

* Update CHANGELOG.md

* Apply suggestions from code review

Co-authored-by: Joel Speed <Joel.speed@hotmail.co.uk>

* Set CreatedAt to Now() on token refresh

Co-authored-by: Joel Speed <Joel.speed@hotmail.co.uk>

* Allow complex structure for groups in group claim.

* Remove unused constant

* Update variable name

* Fix linting

* Use helper method

* Log error if not possible to append group value

* Add missing import

* Use own logger

* Fix imports

* Remove Dockerfile for testing

* Add Changelog entry

* Use formatGroup helper method and update tests

* Return string instead of string array

* Remove groups variable

* Return error in format method.

* Reorder imports

Co-authored-by: Nick Meves <nick.meves@greenhouse.io>

Fix typo in README.md

Refactor redeemCode and support a Provider-wide EnrichSessionState method

This is handled globally

i.e. that the token must have a recognized `aud` field.

* Document set_xauthrequest with pass_access_token

Document feature implemented in https://github.com/oauth2-proxy/oauth2-proxy/pull/68

The feature is already decribed in in the nginx example but not clearly
on each respective parameters documentation.

* Update docs/configuration/configuration.md

Co-authored-by: Nick Meves <nick.meves@greenhouse.io>

Co-authored-by: Nick Meves <nick.meves@greenhouse.io>

Fix code coverage reporting on GitHub actions

* simplify github actions workflow

no more GOPATH, update Go to 1.15.x

* add script to install golangci-lint

* drop support for Go 1.14

* check docker build in ci

* update alpine linux to 3.12

* update CHANGELOG

* fix golangci-lint installation

Co-authored-by: Joel Speed <Joel.speed@hotmail.co.uk>

Add generic Header injectors for upstream request and response headers

Support HTTP method based allowlists