Return connection error for activation

What does this MR do?

We want to let the frontend know about connection issues during the activation phase, so they can inform the admin.

Connectivity errors will be represented by CONNECTIVITY_ERROR string.

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because this is a developing feature guarded by feature flag.
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Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.

Related to #327255