Onboard Intake(3/3): introduce Intake Users

[yago-123]

Description

Intake is composed of three components:

• Intake Runners: dedicated, isolated runtime data ingestion environment
• Intakes: a specific data stream or topic within an Intake Runner
• Intake Users: provides secure access credentials for your applications to connect to your Intake.

Intake Runner and Intakes has already been merged (#952, #1124) this PR is the continuation and last module for fully onboarding Intake into the CLI.

relates to #1234

Checklist

• Issue was linked above
• Code format was applied: make fmt
• Examples were added / adjusted (see e.g. here)
• Docs are up-to-date: make generate-docs (will be checked by CI)
• Unit tests got implemented or updated
• Unit tests are passing: make test (will be checked by CI)
• No linter issues: make lint (will be checked by CI)

[yago-123]

@rubenhoenle thanks for the quick review. For the subcommand declaraction I adjusted Intake Runner aswell to match the pattern.

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[yago-123]

Bot keep this open please

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[github-actions]

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[yago-123]

Thank you both🙏🏻 included the changes and tested the new spinner