fetch all roles for matrix

[andreasfrisch]

💡 Reason:
Frontend received too few roles for the permission matrix, due to our filtering of assignable roles

🌟 Changes:

• Create internal function for fetching all roles
• Create two helper functions for returning roles to outside calls, based on internal function

[DFDS-Snyk]

✅ Snyk checks have passed. No issues have been found so far.

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✅	Open Source Security	0	0	0	0	0 issues
✅	Licenses	0	0	0	0	0 issues
✅	Code Security	0	0	0	0	0 issues

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