[WIP] Check that a user belongs to the correct SHM domain when registering with an SRE

[craddm]

…with SRE

✅ Checklist

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🚦 Depends on

⤴️ Summary

Adds a check of the user's principal name when registering with an SRE. If the domain in the principal name does not match the FQDN of the SHM that the SRE is linked to, the user will not be added to the SRE's security group and an error will be printed explaining why.

🌂 Related issues

Closes #2275

🔬 Tests

Tested locally

[github-actions]

Coverage report

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
data_safe_haven/commands
users.py					150-164
Project Total

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