Reuse system-access in backend-proxy-middleware

[tobiasqueck]

• enhance system-access with refreshToken handling as it is in the backend-proxy-middleware
• replace backend-proxy-middleware code that accesses a system with system-access
• enhance and refactor the unit tests

[changeset-bot]

⚠️ No Changeset found

Latest commit: d7065d6

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[sonarcloud]

Quality Gate failed

Failed conditions
72.0% Coverage on New Code (required ≥ 80%)

See analysis details on SonarCloud