Retrieve real version of PCloud tenant as part of `psPASFormat` parameter for `Get-IdentityHeader` in `IdentityAuth.psm1`

[aaearon]

Desired Outcome

Currently the version used when creating a psPAS.CyberArk.Vault.Session is hardcoded to be 12.6. The psPAS module uses this property to determine if the PAS version has the needed functionality. This PR makes it so the real version of the PCloud tenant is used as the ExternalVersion property when creating psPAS.CyberArk.Vault.Session.

Implemented Changes

The function now retrieves the real ExternalVersion of the PCloud tenant and uses it when creating the psPAS.CyberArk.Vault.Session object.

Connected Issue/Story

n/a

Definition of Done

At least 1 todo must be completed in the sections below for the PR to be merged.

Changelog

• [ ] The CHANGELOG has been updated, or
• [x] This PR does not include user-facing changes and doesn't require a CHANGELOG update

Test coverage

• [ ] This PR includes new unit and integration tests to go with the code changes, or
• [x] The changes in this PR do not require tests

Documentation

• [ ] Docs (e.g. READMEs) were updated in this PR
• [ ] A follow-up issue to update official docs has been filed here: [insert issue ID]
• [x] This PR does not require updating any documentation

Behavior

• [ ] This PR changes product behavior and has been reviewed by a PO, or
• [ ] These changes are part of a larger initiative that will be reviewed later, or
• [x] No behavior was changed with this PR

Security

• [ ] Security architect has reviewed the changes in this PR,
• [ ] These changes are part of a larger initiative with a separate security review, or
• [x] There are no security aspects to these changes