Add mutation to lock/unlock project paths

What does this MR do?

Contributes to #330406 (closed)

This MR adds a mutation to GraphQL API that allows to lock/unlock files in the project.

Lock	Unlock

An example query for testing

mutation {
 projectSetLocked(input: {
    projectPath: "root/my-awesome-project", 
    filePath: "test.pdf",
    lock: true
  }) {
    project {
      pathLocks {
        nodes {
          path
        }
      }
    }
    errors
  } 
}

Screenshots or Screencasts (strongly suggested)

Does this MR meet the acceptance criteria?

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