Explanation
To manually approve or reject request access when registering a client application with an existing API instance or API Group instance, it is required to configure the SLA tier for the application and have one of the following roles or permissions: Organization Administrator, API Manager Environment Administrator, or Manage Contracts permission. These roles or permissions allow managing client applications and contracts in API Manager. References:
https://docs.mulesoft.com/api-manager/2.x/client-applications#managing-client-applications-and-contracts

Explanation
To enable mTLS authentication for HTTP Listener, the developer needs to set an appropriate keystore and truststore configuration for the listener. The keystore contains the certificate and private key of the Mule application that are used to prove its identity to clients. The truststore contains the certificates of trusted clients that are allowed to access the Mule application. References:
https://docs.mulesoft.com/mule-runtime/4.3/tls-configuration#mutual-authentication

Explanation
To give a partial successful response in case the United Airlines API returns with a timeout, the developer should add a Scatter-Gather component inside a Try scope, and set the payload to a default value 'Error' inside the error handler using the On Error Continue scope. A Scatter-Gather component allows sending multiple requests concurrently and aggregating the responses into an array. A Try scope allows handling errors that occur within it using an error handler. An On Error Continue scope allows continuing the flow execution after handling an error. Therefore, by using these components, the developer can send requests to both APIs in parallel, handle any timeout errors from United Airlines API, and return a partial response with a default value for that API. References: https://docs.mulesoft.com/mule-runtime/4.3/scatter-gather-concept
https://docs.mulesoft.com/mule-runtime/4.3/try-scope-concept
https://docs.mulesoft.com/mule-runtime/4.3/on-error-continue-concept

Explanation
The HTTP Request operation will use the default truststore of the JRE to validate the certificate of the target API. If the CA's certificate is present in the truststore, the operation will succeed. Otherwise, it will fail with a handshake exception. References: https://docs.mulesoft.com/mule-runtime/4.3/tls-configuration#tls-default

Explanation
To encrypt the data before sending it to the backend application using PGP encryption, the application needs the public key from the backend service. PGP encryption uses a public-key cryptography system, which means that each party has a pair of keys: a public key and a private key. The public key is used to encrypt data, and the private key is used to decrypt data. Therefore, to encrypt data for a specific recipient (the backend service), the application needs to use the recipient's public key. The recipient can then use its own private key to decrypt the data. References: https://docs.mulesoft.com/mule-runtime/4.3/cryptography-pgp