Add delete group functionality

[fungame2270]

Issue

Closes #97

Reason for this change

this change was so the user can delete a monitor group

Description of changes

In the page monitors group was added a button, in edit mode, to delete a group, when group is deleted their monitors go to their respective deafault group. In the backend the model groupMonitor was changed cascade.all removed because it was deleting the monitors the service update monitor was updated because it tried to delete the group before putting new group in monitor, and it was giving error of key.

Description of how you validated changes

tested interaction in frontend

Checklist

• [x] I have tested my changes locally.
• [ ] I have updated the documentation to reflect my changes.
• [ ] I have added/updated unit tests (if applicable).
• [x] My code adheres to the CONTRIBUTING GUIDE

Aditional Information

[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

[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