Allow case-insensitive comparison for Equals as well just like Contains

[wahmedswl]

fixes #78

[enisn]

Thanks for you effort, I'll merge it after creating at least a test for this case

[Copilot]

Pull Request Overview

This PR adds a new attribute to perform case-insensitive equality comparisons on string fields and covers it with unit tests.

• Implement ToLowerEqualsComparisonAttribute to generate ToLower().Equals(...) expressions.
• Add BookFilter_LowerEquals and extensive tests for various string matching scenarios.
• Ensure filters behave correctly for nulls, empty strings, whitespace, special and Unicode characters.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
tests/AutoFilterer.Tests/Attributes/ToLowerEqualsComparisonAttributeTests.cs	New tests for case-insensitive equals scenarios across multiple edge cases.
src/AutoFilterer/Attributes/ToLowerEqualsComparisonAttribute.cs	Attribute implementation that builds the expression tree for the equals comparison.

Comments suppressed due to low confidence (2)

tests/AutoFilterer.Tests/Attributes/ToLowerEqualsComparisonAttributeTests.cs:117

• [nitpick] The test name suggests trimming whitespace, but the implementation only compares the raw strings. Either rename the test to clarify it’s exact-match with whitespace or add Trim() in the attribute to actually handle leading/trailing spaces.

    public void BuildExpression_ShouldHandleWhitespace(List<Book> dummyData)

tests/AutoFilterer.Tests/Attributes/ToLowerEqualsComparisonAttributeTests.cs:204

• [nitpick] The filter class name uses an underscore in PascalCase; consider renaming to BookFilterLowerEquals to match standard C# naming conventions.

public class BookFilter_LowerEquals : FilterBase