Add integer function to EPSG and ESRI types

[juliohm]

Utility function to extract integer from code types.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.15%. Comparing base (525c1be) to head (95705c1).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #333   +/-   ##
=======================================
  Coverage   92.14%   92.15%           
=======================================
  Files          40       40           
  Lines        1807     1809    +2     
=======================================
+ Hits         1665     1667    +2     
  Misses        142      142           

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[Copilot]

Pull request overview

This PR adds a utility function integer to extract the integer value from EPSG and ESRI code types. This provides a convenient way to retrieve the numeric code from parameterized CRSCode types.

Key Changes

• Introduced CoordRefSystems.integer function with implementations for both EPSG{Code} and ESRI{Code} types
• Added comprehensive test coverage for the new functionality
• Reorganized code structure by moving ESRI type definition to group related implementations together

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/codes.jl	Added integer function declaration and implementations for EPSG and ESRI types; reorganized ESRI type definition for better code grouping
test/codes.jl	New test file validating integer extraction from EPSG{4326} and ESRI{102100}
test/runtests.jl	Added new codes.jl test file to the test suite

The implementation follows established patterns in the codebase, with proper documentation format and qualified naming convention (CoordRefSystems.integer). The changes are clean, well-tested, and maintain consistency with the existing API design.

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