Multiple Client Data Providers erases previously provisioned data.

I have a case where both the `@flowfuse/node-red-dashboard-2-user-addon` and `@aikitori/node-red-dashboard-2-authelia-auth` plugins are installed (but in actual fact I was only using the authelia plugin). The authelia plugin runs before the flowfuse plugin and populates the client data on the user correctly, but when the flowfuse plugin runs, it erases the data again.

- What is the policy around having multiple client data providers?
- Is there a way to specify the order in which they should run?

Start by tracing how the @aikitori/node-red-dashboard-2-authelia-auth and @flowfuse/node-red-dashboard-2-user-addon plugins provide and merge client data. Check the provider lifecycle and any existing tests or documentation for multiple providers and execution order. Done means the policy is defined and the observed data loss or ordering limitation is addressed and verified.

Written by the indexing model from the issue text.