Implement specify_fct()

[jonthegeek]

Closes #2.

[Copilot]

Pull Request Overview

This PR implements the specify_fct() function to create factor harmonization specifications. The implementation uses the S7 object system to define a new class hrmn_fct that inherits from factor but serves as a specification object rather than containing actual data.

Key changes:

• Added specify_fct() function using S7 class system with hrmn_fct class
• Created comprehensive test coverage for the new functionality
• Updated package dependencies to include S7

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
R/specify_fct.R	Implements the main specify_fct() function as an S7 class constructor
tests/testthat/test-specify_fct.R	Adds test coverage for class validation and levels storage
tests/testthat/test-dummy.R	Removes placeholder test file
man/specify_fct.Rd	Auto-generated documentation for the new function
R/zzz.R	Adds S7 compatibility for older R versions
NAMESPACE	Exports the new function and imports S7 operator
DESCRIPTION	Updates version and adds S7 dependency

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