Add microsoft oauth2 providers (#16544)

* Clean up oauth2 providers

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Add AzureAD, AzureADv2, MicrosoftOnline OAuth2 providers

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Apply suggestions from code review

* remove unused Scopes

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: techknowlogick <techknowlogick@gitea.io>

vendor/github.com/markbates/goth/providers/microsoftonline/session.go

@@ -0,0 +1,62 @@
+package microsoftonline
+
+import (
+	"encoding/json"
+	"errors"
+	"strings"
+	"time"
+
+	"github.com/markbates/goth"
+)
+
+// Session is the implementation of `goth.Session` for accessing microsoftonline.
+// Refresh token not available for microsoft online: session size hit the limit of max cookie size
+type Session struct {
+	AuthURL     string
+	AccessToken string
+	ExpiresAt   time.Time
+}
+
+// GetAuthURL will return the URL set by calling the `BeginAuth` function on the Facebook provider.
+func (s Session) GetAuthURL() (string, error) {
+	if s.AuthURL == "" {
+		return "", errors.New(goth.NoAuthUrlErrorMessage)
+	}
+
+	return s.AuthURL, nil
+}
+
+// Authorize the session with Facebook and return the access token to be stored for future use.
+func (s *Session) Authorize(provider goth.Provider, params goth.Params) (string, error) {
+	p := provider.(*Provider)
+	token, err := p.config.Exchange(goth.ContextForClient(p.Client()), params.Get("code"))
+	if err != nil {
+		return "", err
+	}
+
+	if !token.Valid() {
+		return "", errors.New("Invalid token received from provider")
+	}
+
+	s.AccessToken = token.AccessToken
+	s.ExpiresAt = token.Expiry
+
+	return token.AccessToken, err
+}
+
+// Marshal the session into a string
+func (s Session) Marshal() string {
+	b, _ := json.Marshal(s)
+	return string(b)
+}
+
+func (s Session) String() string {
+	return s.Marshal()
+}
+
+// UnmarshalSession wil unmarshal a JSON string into a session.
+func (p *Provider) UnmarshalSession(data string) (goth.Session, error) {
+	session := &Session{}
+	err := json.NewDecoder(strings.NewReader(data)).Decode(session)
+	return session, err
+}