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/going/defaults/defaults.go

@@ -0,0 +1,36 @@
+package defaults
+
+func String(s1, s2 string) string {
+	if s1 == "" {
+		return s2
+	}
+	return s1
+}
+
+func Int(i1, i2 int) int {
+	if i1 == 0 {
+		return i2
+	}
+	return i1
+}
+
+func Int64(i1, i2 int64) int64 {
+	if i1 == 0 {
+		return i2
+	}
+	return i1
+}
+
+func Float32(i1, i2 float32) float32 {
+	if i1 == 0.0 {
+		return i2
+	}
+	return i1
+}
+
+func Float64(i1, i2 float64) float64 {
+	if i1 == 0.0 {
+		return i2
+	}
+	return i1
+}