all: refactor handler logic

- all: prefer `FormValues` to `ParseForm` with subsequent `Form.Get`s
- all: refactor authentication stack to be checked by middleware, and accessible via request context.
- all: replace http.ServeMux with gorilla/mux’s router
- all: replace custom CSRF checks with gorilla/csrf middleware
- authenticate: extract callback path as constant.
- internal/config: implement stringer interface for policy
- internal/cryptutil: add helper func `NewBase64Key`
- internal/cryptutil: rename `GenerateKey` to `NewKey`
- internal/cryptutil: rename `GenerateRandomString` to `NewRandomStringN`
- internal/middleware: removed alice in favor of gorilla/mux
- internal/sessions: remove unused `ValidateRedirectURI` and `ValidateClientSecret`
- internal/sessions: replace custom CSRF with gorilla/csrf fork that supports custom handler protection
- internal/urlutil: add `SignedRedirectURL` to create hmac'd URLs
- internal/urlutil: add `ValidateURL` helper to parse URL options
- internal/urlutil: add `GetAbsoluteURL` which takes a request and returns its absolute URL.
- proxy: remove holdover state verification checks; we no longer are setting sessions in any proxy routes so we don’t need them.
- proxy: replace un-named http.ServeMux with named domain routes.

Signed-off-by: Bobby DeSimone <bobbydesimone@gmail.com>

internal/sessions/mock_store.go

@@ -4,28 +4,6 @@ import (
 	"net/http"
 )
 
-// MockCSRFStore is a mock implementation of the CSRF store interface
-type MockCSRFStore struct {
-	ResponseCSRF string
-	Cookie       *http.Cookie
-	GetError     error
-}
-
-// SetCSRF sets the ResponseCSRF string to a val
-func (ms MockCSRFStore) SetCSRF(rw http.ResponseWriter, req *http.Request, val string) {
-	ms.ResponseCSRF = val
-}
-
-// ClearCSRF clears the ResponseCSRF string
-func (ms MockCSRFStore) ClearCSRF(http.ResponseWriter, *http.Request) {
-	ms.ResponseCSRF = ""
-}
-
-// GetCSRF returns the cookie and error
-func (ms MockCSRFStore) GetCSRF(*http.Request) (*http.Cookie, error) {
-	return ms.Cookie, ms.GetError
-}
-
 // MockSessionStore is a mock implementation of the SessionStore interface
 type MockSessionStore struct {
 	ResponseSession string