feat(DTFS2-7449): add cancel cancellation POST endpoint

[MarRobSoftwire]

Introduction :pencil2:

Yes, Cancel button should make a POST request & delete the cancellation, the No button should redirect the user to the previous page.

Resolution :heavy_check_mark:

• Add new POST endpoint
• Update the nunjucks template so the No button is handled correctly
• Add unit test coverage

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

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

See analysis details on SonarCloud