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>

services/auth/source/oauth2/providers_simple.go

@@ -0,0 +1,108 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package oauth2
+
+import (
+	"code.gitea.io/gitea/modules/setting"
+
+	"github.com/markbates/goth"
+	"github.com/markbates/goth/providers/azuread"
+	"github.com/markbates/goth/providers/bitbucket"
+	"github.com/markbates/goth/providers/discord"
+	"github.com/markbates/goth/providers/dropbox"
+	"github.com/markbates/goth/providers/facebook"
+	"github.com/markbates/goth/providers/google"
+	"github.com/markbates/goth/providers/microsoftonline"
+	"github.com/markbates/goth/providers/twitter"
+	"github.com/markbates/goth/providers/yandex"
+)
+
+// SimpleProviderNewFn create goth.Providers without custom url features
+type SimpleProviderNewFn func(clientKey, secret, callbackURL string, scopes ...string) goth.Provider
+
+// SimpleProvider is a GothProvider which does not have custom url features
+type SimpleProvider struct {
+	BaseProvider
+	scopes []string
+	newFn  SimpleProviderNewFn
+}
+
+// CreateGothProvider creates a GothProvider from this Provider
+func (c *SimpleProvider) CreateGothProvider(providerName, callbackURL string, source *Source) (goth.Provider, error) {
+	return c.newFn(source.ClientID, source.ClientSecret, callbackURL, c.scopes...), nil
+}
+
+// NewSimpleProvider is a constructor function for simple providers
+func NewSimpleProvider(name, displayName string, scopes []string, newFn SimpleProviderNewFn) *SimpleProvider {
+	return &SimpleProvider{
+		BaseProvider: BaseProvider{
+			name:        name,
+			displayName: displayName,
+		},
+		scopes: scopes,
+		newFn:  newFn,
+	}
+}
+
+var _ (GothProvider) = &SimpleProvider{}
+
+func init() {
+	RegisterGothProvider(
+		NewSimpleProvider("bitbucket", "Bitbucket", []string{"account"},
+			func(clientKey, secret, callbackURL string, scopes ...string) goth.Provider {
+				return bitbucket.New(clientKey, secret, callbackURL, scopes...)
+			}))
+
+	RegisterGothProvider(
+		NewSimpleProvider("dropbox", "Dropbox", nil,
+			func(clientKey, secret, callbackURL string, scopes ...string) goth.Provider {
+				return dropbox.New(clientKey, secret, callbackURL, scopes...)
+			}))
+
+	RegisterGothProvider(NewSimpleProvider("facebook", "Facebook", nil,
+		func(clientKey, secret, callbackURL string, scopes ...string) goth.Provider {
+			return facebook.New(clientKey, secret, callbackURL, scopes...)
+		}))
+
+	// named gplus due to legacy gplus -> google migration (Google killed Google+). This ensures old connections still work
+	RegisterGothProvider(NewSimpleProvider("gplus", "Google", []string{"email"},
+		func(clientKey, secret, callbackURL string, scopes ...string) goth.Provider {
+			if setting.OAuth2Client.UpdateAvatar || setting.OAuth2Client.EnableAutoRegistration {
+				scopes = append(scopes, "profile")
+			}
+			return google.New(clientKey, secret, callbackURL, scopes...)
+		}))
+
+	RegisterGothProvider(NewSimpleProvider("twitter", "Twitter", nil,
+		func(clientKey, secret, callbackURL string, scopes ...string) goth.Provider {
+			return twitter.New(clientKey, secret, callbackURL)
+		}))
+
+	RegisterGothProvider(NewSimpleProvider("discord", "Discord", []string{discord.ScopeIdentify, discord.ScopeEmail},
+		func(clientKey, secret, callbackURL string, scopes ...string) goth.Provider {
+			return discord.New(clientKey, secret, callbackURL, scopes...)
+		}))
+
+	// See https://tech.yandex.com/passport/doc/dg/reference/response-docpage/
+	RegisterGothProvider(NewSimpleProvider("yandex", "Yandex", []string{"login:email", "login:info", "login:avatar"},
+		func(clientKey, secret, callbackURL string, scopes ...string) goth.Provider {
+			return yandex.New(clientKey, secret, callbackURL, scopes...)
+		}))
+
+	RegisterGothProvider(NewSimpleProvider(
+		"azuread", "Azure AD", nil,
+		func(clientID, secret, callbackURL string, scopes ...string) goth.Provider {
+			return azuread.New(clientID, secret, callbackURL, nil, scopes...)
+		},
+	))
+
+	RegisterGothProvider(NewSimpleProvider(
+		"microsoftonline", "Microsoft Online", nil,
+		func(clientID, secret, callbackURL string, scopes ...string) goth.Provider {
+			return microsoftonline.New(clientID, secret, callbackURL, scopes...)
+		},
+	))
+
+}