Validate Storage Capacity Before Volume Create

[sp16743]

Description

This PR adds a storage-capacity check when creating a volume on an explicitly selected primary storage pool.

Previously, this path could attempt volume creation without validating the pool’s available over-provisioned capacity. The change rejects the request when the selected pool does not have enough space.

Fixes: #14313

Types of changes

• Breaking change (fix or feature that would cause existing functionality to change)
• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Enhancement (improves an existing feature and functionality)
• Cleanup (Code refactoring and cleanup, that may add test cases)
• Build/CI
• Test (unit or integration test code)

Feature/Enhancement Scale or Bug Severity

Feature/Enhancement Scale

• Major
• Minor

Bug Severity

• BLOCKER
• Critical
• Major
• Minor
• Trivial

Screenshots (if appropriate):

Before the fix:

After the fix:

How Has This Been Tested?

How did you try to break this feature and the system with this change?

[boring-cyborg]

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[weizhouapache]

there is a similar PR #14071, I will close it, let's focus on this

[codecov]

Codecov Report

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 19.91%. Comparing base (1a48a87) to head (7b51040).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...n/java/com/cloud/storage/VolumeApiServiceImpl.java	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##               main   #14314   +/-   ##
=========================================
  Coverage     19.91%   19.91%           
- Complexity    20199    20200    +1     
=========================================
  Files          6373     6373           
  Lines        577230   577233    +3     
  Branches      70696    70697    +1     
=========================================
+ Hits         114950   114959    +9     
+ Misses       449713   449708    -5     
+ Partials      12567    12566    -1     

Flag	Coverage Δ
uitests	3.71% <ø> (ø)
unittests	21.18% <0.00%> (+<0.01%)	⬆️

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[Damans227]

should this also check how full the pool really is on disk? the other space checks look at that too, but this one only counts space already handed out