This PR fixes several AbstractFilterExpressionConverter implementations that handled String values incorrectly by directly embedding them into the filter expression without proper escaping.

Previously, many converters contained code like:

else if (value instanceof String s) {
    context.append(String.format(“valueText:"%s" “, s));
}

This approach is unsafe because it assumes that s does not contain special characters such as quotes (") or backslashes (\), which can lead to malformed expressions or potential injection issues.

Changes Introduced

• Added proper escaping of String values in all affected converters.
• Ensured that backslashes, quotes, and other special characters are safely encoded before being appended.
• Replaced unsafe string concatenation with safer formatting or helper methods where applicable.

Motivation

This change prevents potential filter expression injection issues and ensures consistent and safe encoding of string literals across all filter expression converters.

Testing

• Added/updated unit tests covering strings with special characters (", \, unicode sequences, etc.).
• Verified that generated filter expressions are syntactically correct and properly escaped.

Related Issue

Fixes #4545

Checklist

• Code builds and all existing tests pass
• Added new test cases for special character handling
• Verified compatibility and no breaking API changes

Example Before / After