Push Rules API 404 when dot in the namespace

What does this MR do and why?

Contributes to #433469 (closed)

Problem

When user directly provides a path to the project or group and the path contains a . symbol. Then the user receives a 404 response even if the push rule exists.

Solution

Add missing requirements for resouces definition.

How to set up and validate locally

1. Create a project with a . in the name. For example, project.path
2. Visit push API link (similar to http://127.0.0.1:3000/api/v4/projects/root%2Fproject.path/push_rule)
3. You should see null if the push rule is not set
4. Without a fix, you will see a 404 error.

MR acceptance checklist

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