Fix/981 max can allocate cannot be negative

[joe-bowman]

1. Summary

Fixes #981

Ensure MaxCanAllocate cannot be negative. Add denfensive checks to DetermineAllocationsForDelegation to ensure safety from under and overflows.

2.Type of change

• Bug fix (non-breaking change which fixes an issue)

3. Implementation details

Add a sdkmath.MaxInt(0, previousVal) to ensure that min is 0 if previousVal was negative.

Add defensive checks in DetermineAllocationsForDelegation to determine that maxCanAllocate is positive (caps cannot be negative) and that overall allocation sum is equal to the input amount.

[codecov]

Codecov Report

Attention: 7 lines in your changes are missing coverage. Please review.

Comparison is base (2783379) 61.75% compared to head (efedaaa) 61.73%.
Report is 1 commits behind head on main.

❗ Current head efedaaa differs from pull request most recent head cf2c987. Consider uploading reports for the commit cf2c987 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #982      +/-   ##
==========================================
- Coverage   61.75%   61.73%   -0.03%     
==========================================
  Files         172      172              
  Lines       14116    14122       +6     
==========================================
  Hits         8718     8718              
- Misses       4651     4656       +5     
- Partials      747      748       +1     

Flag	Coverage Δ
unittests	61.73% <12.50%> (-0.03%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
x/interchainstaking/keeper/delegation.go	92.27% <100.00%> (ø)
x/interchainstaking/types/delegation.go	77.12% <0.00%> (-3.15%)	⬇️