Unix file chmod

[adrazilo]

Proposed changes

This PR addresses Issue: The metadata command is missing from the mock server.

Type of change

• New feature (non-breaking change which adds functionality)

PR Checklist

• If the changes in this PR are meant for the next release / mainline, this PR targets the "staging" branch.
• My code follows the style guidelines of this project (see: Contributing guideline)
• I have commented my code, particularly in hard-to-understand areas
• New and existing unit tests pass locally with my changes
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works, or describe a test method below

Testing

To test this feature, please consider the following test conditions:

1. You attempt to change the mode without including the mode.
2. You attempt to change the mode with a non-octal mode.
3. You attempt to change the mode of a path/file that does not exist.
4. You attempt to change the mode of an existing file/folder without recursion.
5. You attempt to change the mode of a folder with recursion without a pattern.
6. You attempt to change the mode of a folder with recursion with a pattern.

Further comments

This is not a relatively large change but will further enhance the mock server for learning purposes.