Azure-sdk-for-js: Setting certificate properties on import requires an issuer

[heaths]

In track 2 setting certificate properties via CertificatePolicy requires passing an issuer, when in track 1 that was not required.

To support import, define a default constructor but leave Issuer, Subject, and SubjectAlternativeNames read-only properties. The parameters in existing constructors should also continue to be asserted. issuer is optional during import, and subject is ignored - obtained from the X509 certificate anyway. We could also loosen restrictions in the future if needs be.

To note: if we did loosen restrictions later and allowed subject or SAN to be null, the service does return a pretty descriptive error that would help customers diagnose the issue:

{
    "error": {
        "code": "BadParameter",
        "message": "Either subjectName or san must be present"
    }
}

[ramya-rao-a]

@heaths Are we sure we need this in the current milestone which ends tomorrow?

[heaths]

I noted in our Teams channel I was merely adding it in this milestone if it could be done (should be small), but punting it to March is perfectly fine.

[maorleger]

Summarizing our conversation:

In TS land the scenario is a bit different:

• Issuer is already optional
• We do require either subject or SAN

To support import we need to provide a different type that allows users to omit all three when importing a certificate.

• Create: Issuer + (SAN | Subject)
• Import: everything optional

I _think_ we already GA'd with optional issuer so all we can do now is loosen restrictions on (SAN | Subject) when importing to support this scenario.

[sadasant]

@maorleger that sounds good to me!