isValidHandle should be case insenstive

[lopper]

Bug report

Describe the bug

isValidHandle should support both upper and lower case letters. Both upper and lower case values are valid url handles.

System information

Medusa version (including plugins):
Node.js version:
Database:
Operating system:
Browser (if relevant):

Steps to reproduce the behavior

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior

A clear and concise description of what you expected to happen

Screenshots

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Code snippets

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Additional context

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