[11.9] Add custom attribute support to Users

[igittigitt]

Added options to user lookup functions:

• "with_custom_attributes" (true|false) to also get users custom attributes in resulting array
• "custom_attributes" can contain an array of custom attributes to lookup users

Added functions:

• "customAttributes(int $id)" to get all custom attributes defined for the user
• "customAttribute(int $id, string $key)" to get single attribute by name
• "createCustomAttribute(int $id, string $key, string $value)" to add another attribute (key/value)
• "updateCustomAttribute(int $id, string $key, string $value)" to update (or create) an existing attribute
• "removeCustomAttribute(int $id, string $key)" to delete an custom attribute by key

[GrahamCampbell]

Thanks for the PR. I've left some feedback to be addressed.

[GrahamCampbell]

you forgot to encode the key

[GrahamCampbell]

invalid phpdoc

[stale]

This issue has been automatically marked as stale because there has been no recent activity. It will be closed after 30 days if no further activity occurs. Thank you for your contributions.