code: @GetMapping("/sp/idp/metadata")
      public ResponseEntity<String> getFirstIdentityProviderMetadata() {
          val saml2Client = builtClients.findClient(SAML2Client.class);
          if (saml2Client != null) {
              return getSaml2ClientIdentityProviderMetadataResponseEntity(saml2Client);
          }
          return getNotAcceptableResponseEntity();
      }
docs: Gets first idp metadata.
  
  @return the first service provider metadata