Validate organizations.path using regex

What does this MR do and why?

For #410428 (closed)

Now that we have the organizations.path attribute on the Organization model, it is necessary that we validate it with regex, so that reserved keywords or paths not matching our parameters for paths are excluded, and validation errors are thrown in such cases.

This MR adds such a validation for organizations.path, I have added more details as comments below.

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Related to #410428 (closed)