Added url property on get fleet maintained app endpoint

[ksykulev]

Checklist for submitter

for #25251

If some of the following don't apply, delete the relevant line.

• Changes file added for user-visible changes in changes/, orbit/changes/ or ee/fleetd-chrome/changes.
  See Changes files for more information.
• Added/updated automated tests

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.61%. Comparing base (41e8324) to head (575b3e5).
Report is 32 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #25660      +/-   ##
==========================================
+ Coverage   63.59%   63.61%   +0.02%     
==========================================
  Files        1622     1622              
  Lines      155115   155173      +58     
  Branches     4055     4055              
==========================================
+ Hits        98648    98716      +68     
+ Misses      48696    48671      -25     
- Partials     7771     7786      +15     

Flag	Coverage Δ
backend	64.47% <ø> (+0.02%)	⬆️

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