[Identity] Client assertion add token cache persistence (#31129)

To have ClientAssertionCredentialOptions implement
ISupportsTokenCachePersistenceOptions. As a consumer of Identity, Azure
PowerShell is dependent on the Azure Identity library for .NET. Now the
client assertion workflow has increasing usage, so the ask should have
higher priority.

Business Impact:
In the client assertion auth flow, Azure PowerShell customers acquire
the access token with the federated token. The access token must be used
by the subsequent Azure PowerShell cmdlets. We depend on Azure.Identity
to save the tokens to the MSAL cache. As the federated token has a short
lifetime, it's impossible to cache the federated token and
reauthenticate every time a cmdlet is run.

sdk/identity/identity/CHANGELOG.md

@@ -6,6 +6,7 @@
 
 - Added support for the field `refreshAfterTimestamp` in `AccessToken` [#30402](https://github.com/Azure/azure-sdk-for-js/pull/30402)
 - Added support for providing an object ID to `ManagedIdentityCredential`. [#30771](https://github.com/Azure/azure-sdk-for-js/pull/30771)
+- Added support for token cache persistence via the `CredentialTokenPersistence` options to the `ClientAssertionCredential`. [#31129](https://github.com/Azure/azure-sdk-for-js/pull/31129)
 
 ### Breaking Changes
 

sdk/identity/identity/review/identity.api.md

@@ -177,7 +177,7 @@ export class ClientAssertionCredential implements TokenCredential {
 }
 
 // @public
-export interface ClientAssertionCredentialOptions extends MultiTenantTokenCredentialOptions, AuthorityValidationOptions {
+export interface ClientAssertionCredentialOptions extends MultiTenantTokenCredentialOptions, CredentialPersistenceOptions, AuthorityValidationOptions {
 }
 
 // @public

sdk/identity/identity/src/credentials/clientAssertionCredentialOptions.ts

@@ -2,6 +2,7 @@
 // Licensed under the MIT License.
 
 import { AuthorityValidationOptions } from "./authorityValidationOptions";
+import { CredentialPersistenceOptions } from "./credentialPersistenceOptions";
 import { MultiTenantTokenCredentialOptions } from "./multiTenantTokenCredentialOptions";
 
 /**
@@ -9,4 +10,5 @@ import { MultiTenantTokenCredentialOptions } from "./multiTenantTokenCredentialO
  */
 export interface ClientAssertionCredentialOptions
   extends MultiTenantTokenCredentialOptions,
+    CredentialPersistenceOptions,
     AuthorityValidationOptions {}