Generate an audit event if policy.yml becomes invalidated
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* Generate an audit event if policy.yml becomes invalidated
## Verification steps
1. Create a project
2. Navigate to "Secure =\> Policies" and create a security policy with a merge request.
3. Manually edit the `policy.yml` in the merge request and make it invalid
4. Merge the MR with invalid `policy.yml` file
5. Verify an audit event of type `policy_yaml_invalidated `is recorded.
task