[Security Solution][Notes] - unskip and add new api integration tests

[PhilippeOberti]

Description

There are a couple of notes api integration tests that are currently skipped. There are 2 challenges currently:

• retrieve the uid of a user (the logged-in user or any created user). The username can easily be retrieved (from here on ess and here on serverless) but it does seem that there is currently a way to retrieve the entire user object.

Notes: it seems that we might be able to retrieve the user information using the saml auth service (const saml = getService('samlAuth'))

• create more users so we can test filtering by different users and retrieve the notes only for that user

There are also a few TODOs a the bottom of the file to write more tests.

Notes

We're planning on making some drastic api changes for all the notes endpoints, so waiting for that might be a good idea...

Acceptance criteria

• unskip the skipped tests
• add new tests to have no TODOs left

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Pinging @elastic/security-solution (Team: SecuritySolution)

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Pinging @elastic/security-threat-hunting (Team:Threat Hunting)