fix: pass sessionID to OTP email link (#8745)

# Which Problems Are Solved

OTP Email links currently could not use / include the sessionID they
belong to. This prevents an easy use for redirecting and handling OTP
via email through the session API.

# How the Problems Are Solved

Added the sessionID as placeholder for the OTP Email link template.

# Additional Changes

List all available placeholders in the url_templates of V2 endpoints.

# Additional Context

- discussed in a customer meeting

internal/domain/session.go

@@ -20,16 +20,18 @@ type OTPEmailURLData struct {
 	LoginName         string
 	DisplayName       string
 	PreferredLanguage language.Tag
+	SessionID         string
 }
 
 // RenderOTPEmailURLTemplate parses and renders tmpl.
 // code, userID, (preferred) loginName, displayName and preferredLanguage are passed into the [OTPEmailURLData].
-func RenderOTPEmailURLTemplate(w io.Writer, tmpl, code, userID, loginName, displayName string, preferredLanguage language.Tag) error {
+func RenderOTPEmailURLTemplate(w io.Writer, tmpl, code, userID, loginName, displayName, sessionID string, preferredLanguage language.Tag) error {
 	return renderURLTemplate(w, tmpl, &OTPEmailURLData{
 		Code:              code,
 		UserID:            userID,
 		LoginName:         loginName,
 		DisplayName:       displayName,
 		PreferredLanguage: preferredLanguage,
+		SessionID:         sessionID,
 	})
 }