[IMP] cmis_alf: support backend location override

[sbidoul]

Depends on OCA/connector-cmis#49

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 73.37%. Comparing base (c6c1822) to head (24d1cde).
⚠️ Report is 22 commits behind head on 16.0.

Files with missing lines	Patch %	Lines
cmis_alf/models/cmis_backend.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             16.0     #199       +/-   ##
===========================================
- Coverage   86.71%   73.37%   -13.34%     
===========================================
  Files          33       53       +20     
  Lines        1061     1435      +374     
  Branches      124      149       +25     
===========================================
+ Hits          920     1053      +133     
- Misses        117      361      +244     
+ Partials       24       21        -3     

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