[Task]: Create service accounts for the scanner pipeline

[willdurand]

Description

We would like to be able to create service accounts, which:

1. cannot log in (and do not have a FxA ID)
2. can be easily identified as service accounts
3. have API keys that we can rotate easily

Acceptance Criteria

see above

┆Issue is synchronized with this Jira Task

[diox]

Rough idea: automatically create a service account when registering a scanner pipeline.

The account should not have an email or fxa id so that it can't log in.