Introduce status field to Device model for better representation of state

[Steve-Mcl]

Description

This pull request adds a new virtual status field to the Device model and introduces comprehensive unit tests to verify its behavior. The main goal is to provide a simple way to determine if a device is "online", "offline", or "not-seen" based on the lastSeenAt timestamp.

Device model enhancements:

• Added a virtual status field to the Device model, which returns "not-seen" if the device has never been seen, "online" if seen within the last 30 minutes, and "offline" otherwise.

Testing improvements:

• Added unit tests for the new status virtual field in Device_spec.js, covering all possible status values ("not-seen", "online", "offline") based on different lastSeenAt values.

Related Issue(s)

closes #7826

Checklist

• I have read the contribution guidelines
• Suitable unit/system level tests have been added and they pass
• Documentation has been updated
  • Upgrade instructions
  • Configuration details
  • Concepts
• Changes flowforge.yml?
  • Issue/PR raised on FlowFuse/helm to update ConfigMap Template
  • Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production
• Link to Changelog Entry PR, or note why one is not needed.

Labels

• Includes a DB migration? -> add the area:migration label

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.10%. Comparing base (a7b9f86) to head (5cc2cee).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7828   +/-   ##
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  Coverage   75.09%   75.10%           
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  Files         430      430           
  Lines       22838    22844    +6     
  Branches     6052     6054    +2     
=======================================
+ Hits        17151    17157    +6     
  Misses       5687     5687           

Flag	Coverage Δ
backend	75.10% <100.00%> (+<0.01%)	⬆️

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[Steve-Mcl]

odd - unrelated UI test error

  1) FlowFuse platform admin users
       can view applications and instances from teams they're not a member of:
     AssertionError: Timed out retrying after 4000ms: expected 'http://localhost:3001/team/bteam/overview' to include '/applications'
      at Context.eval (webpack:///../test/e2e/frontend/cypress/tests/admin.spec.js:78:17)

Re-running

[andypalmi]

Looks good to me. Good job on the new test

[knolleary]

I was expecting this to include updates to the Device Views to include this new field - I assumed the MCP stuff would be accessing things via the external platform API.

If that isn't going to get covered here, please add a note to the UI issue you raised to point out the UI doesn't yet have visibility of the new field.

[Steve-Mcl]

I was expecting this to include updates to the Device Views to include this new field - I assumed the MCP stuff would be accessing things via the external platform API.

If that isn't going to get covered here, please add a note to the UI issue you raised to point out the UI doesn't yet have visibility of the new field.

For MCP stuff, no FE (or views) are required so no, not done in this one. I'll tip a wink to the requirement for views in the 2nd sub-task (which is small enough to be a single PR or broken down further into FE and BE tasks)