Use FILE_SERVICE_URI that allows for full URI

[Adirael]

Description

Allows setting a full URI to interact with the VIP File System

Changelog Description

Changed

• Renamed global variable that contains the VIP File System endpoint

Pre-review checklist

Please make sure the items below have been covered before requesting a review:

• This change works and has been tested locally or in Codespaces (or has an appropriate fallback).
• This change works and has been tested on a sandbox.
• This change has relevant unit tests (if applicable).
• This change uses a rollout method to ease with deployment (if applicable - especially for large scale actions that require writes).
• This change has relevant documentation additions / updates (if applicable).
• I've created a changelog description that aligns with the provided examples.

Pre-deploy checklist

• VIP staff: Ensure any alerts added/updated conform to internal standards (see internal documentation).

Steps to Test

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 30.44%. Comparing base (74d2acf) to head (480e22f).

Files with missing lines	Patch %	Lines
a8c-files.php	0.00%	2 Missing ⚠️
files/class-api-client.php	0.00%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #6195      +/-   ##
=============================================
+ Coverage      30.42%   30.44%   +0.01%     
  Complexity      4826     4826              
=============================================
  Files            290      290              
  Lines          21329    21317      -12     
=============================================
  Hits            6489     6489              
+ Misses         14840    14828      -12     

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