fix: improve login_hint usage on IDPs (#6899)

* only set prompt if no login_hint is set

* update to current state and cleanup

internal/idp/provider.go

@@ -11,7 +11,7 @@ import (
 // Provider is the minimal implementation for a 3rd party authentication provider
 type Provider interface {
 	Name() string
-	BeginAuth(ctx context.Context, state string, params ...any) (Session, error)
+	BeginAuth(ctx context.Context, state string, params ...Parameter) (Session, error)
 	IsLinkingAllowed() bool
 	IsCreationAllowed() bool
 	IsAutoCreation() bool
@@ -34,3 +34,18 @@ type User interface {
 	GetAvatarURL() string
 	GetProfile() string
 }
+
+// Parameter allows to pass specific parameter to the BeginAuth function
+type Parameter interface {
+	setValue()
+}
+
+// UserAgentID allows to pass the user agent ID of the auth request to BeginAuth
+type UserAgentID string
+
+func (p UserAgentID) setValue() {}
+
+// LoginHintParam allows to pass a login_hint to BeginAuth
+type LoginHintParam string
+
+func (p LoginHintParam) setValue() {}