imp: claims invariants

[fedekunze]

Description

Closes: #XXX

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PR review checkboxes:

I have...

• added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• included the correct type prefix in the PR title
• targeted the correct branch (see PR Targeting)
• provided a link in the PR description to the relevant issue or specification
• reviewed "Files changed" and left comments if necessary
• confirmed all required CI checks have passed

Code maintenance:

I have...

• written unit and integration tests
• added relevant godoc and code comments.
• updated relevant documentation (docs/) or specification (x/<module>/spec/)

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Reviewers Checklist

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I have...

• confirmed the correct type prefix in the PR title
• confirmed all author checklist items have been addressed
• confirmed that this PR does not change production code

[codecov]

Codecov Report

Merging #385 (935c0ff) into main (daf5b06) will increase coverage by 0.22%.
The diff coverage is 100.00%.

❗ Current head 935c0ff differs from pull request most recent head c57b9b6. Consider uploading reports for the commit c57b9b6 to get more accurate results

@@            Coverage Diff             @@
##             main     #385      +/-   ##
==========================================
+ Coverage   78.17%   78.40%   +0.22%     
==========================================
  Files          93       94       +1     
  Lines        5456     5514      +58     
==========================================
+ Hits         4265     4323      +58     
  Misses       1035     1035              
  Partials      156      156              

Impacted Files	Coverage Δ
x/claims/keeper/claim.go	100.00% <100.00%> (ø)
x/claims/keeper/grpc_query.go	84.41% <100.00%> (+0.41%)	⬆️
x/claims/keeper/invariants.go	100.00% <100.00%> (ø)

[danburck]

Nice, left minor comments