fix(approval): send mail and notification to requester

[Phil91]

Description

Adjust the mail and notification creation to create them for the requesting user instead of the calling user.

Why

Since the calling user is the operator, the requesting user is currently not informed about the approval / rejection of the credentials.

Issue

Refs: eclipse-tractusx/portal-backend#712

Corresponding Portal PR

713

Checklist

• I have followed the contributing guidelines
• I have performed IP checks for added or updated 3rd party libraries
• I have created and linked IP issues or requested their creation by a committer
• I have performed a self-review of my own code
• I have successfully tested my changes locally
• I have added tests that prove my changes work
• I have checked that new and existing tests pass locally with my changes
• I have commented my code, particularly in hard-to-understand areas
• I have added copyright and license headers, footers (for .md files) or files (for images)

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud