docs: public void setSigningKey(String key) {
  		Assert.hasText(key);
  		key = key.trim();
  
  		this.signingKey = key;
  
  		if (isPublic(key)) {
  			signer = new RsaSigner(key);
  			logger.info("Configured with RSA signing key");
  		}
  		else {
  			// Assume it's a MAC key
  			this.verifierKey = key;
  			signer = new MacSigner(key);
  		}
  	}