[Identity] Align with samples in other languages

[sadasant]

Other languages have specific samples that show recent features that we are currently adding to Identity, so we don't have these samples yet in our repo.

One place to look for is on the .Net samples folder: https://github.com/Azure/azure-sdk-for-net/tree/master/sdk/identity/Azure.Identity

This is related to: #13788

[sadasant]

@maorleger recently updated the JavaScript samples. He specifically added AzureIdentityExamples.md, which covers many of the sample cases in other languages. .Net has samples in a different way. Here's a list of the topics that .Net shows in samples, and how many of them we have currently covered:

Sample about	Done in JS?	Language that has this
DefaultAzureCredential	Yes	Java
User assigned managed identity with DAC	Yes	Java
Authenticating Azure with managed identity	Yes	Java
Authenticating With Azure Stack using Azure identity	Yes	Java
ClientSecretCredential	Yes	Java
ClientCertificateCredential	Yes	.Net
ClientCertificateCredential with a Key Vault certificate	TODO	Python
Rolling certificates with ClientCertificateCredential	TODO	.Net
InteractiveBrowserCredential	Yes	.Net, Java
DeviceCodeCredential	Yes	.Net, Java
UsernamePasswordCredential	Yes	Java
AuthorizationCodeCredential	Yes	Java
AzureCliCredential	Yes	Java
VisualStudioCodeCredential	Yes	Java
Controlling user authentication	TODO	.Net
Persisting the token cache	TODO	.Net
Named token cache	TODO	.Net
Unencrypted cache	TODO	.Net
AuthenticationRecord	TODO	.Net
Silent authentication	TODO	.Net
Custom credentials	TODO	.Net
Using MSAL directly	TODO	.Net
On Behalf Of Flow	TODO	.Net

Based on this, I'll be adding different sets of documentation samples on both v1 and v2.

Sample about	v1	v2	Status
Rolling certificates with ClientCertificateCredential	Yes	Yes	v1 PR
ClientCertificateCredential with a Key Vault certificate	Yes	Yes	v1 PR
Controlling user authentication	No	Yes	Pending
Persisting the token cache	No	Yes	Pending
Named token cache	No	Yes	Pending
Unencrypted cache	No	Yes	Pending
AuthenticationRecord	No	Yes	Pending
Silent authentication	No	Yes	Pending
Custom credentials	Yes	Yes	v1 PR
Using MSAL directly	Yes	Yes	v1 PR
On Behalf Of Flow	Yes	Yes	v1 PR

[sadasant]

Moved to the July Milestone

[sadasant]

We’ve merged the v1 samples. For the v2 samples, let’s work on them next month, while we work on the user studies.

[sadasant]

TODO

There’s another sample we’re missing:

• We need documentation about how to work with foreign clouds.
• We could provide a sample on how to work with foreign clouds, this sample would mention how to specify the authorityHost property on our credentials.
• We should mention this sample in the README somewhere.
• Related to: Unable to use TokenCredentials instances from the azure/identity library in ServiceClientCredential based SDK's for Sovereign Azure Clouds #15945