feat: add basic structure of idp templates (#5053)

add basic structure and implement first providers for IDP templates to be able to manage and use them in the future

internal/idp/session.go

@@ -0,0 +1,11 @@
+package idp
+
+import (
+	"context"
+)
+
+// Session is the minimal implementation for a session of a 3rd party authentication [Provider]
+type Session interface {
+	GetAuthURL() string
+	FetchUser(ctx context.Context) (User, error)
+}