Option to toggle strict class name matching in parser

This request concerns the parser functionality of Hydrus where multi-value properties such as class have multiple values in a string. This behavior is not found in other properties as its likely due to how the selector/parser handles class selection.

Example

<a class="a b" href="/" > Link </a>

Current Behavior

Content parsers finds a match of the example a tag above if the key-value filter is set to class="a". This is an often desired behavior of parsers and enables tag selection with mixed static and dynamic class names to allow matching a subset of a tag's classes.

Desired Feature/Behavior

Content parsers should have an option to toggle strict/exact matching for class names to allow for strict matching such that the above example matches only with class="a b" and not class="a". This is useful is cases such as parsing tags from pages.

Start by locating Hydrus's content parser implementation and the existing class key-value matching behavior. Confirm how a strict-matching option would be configured, then add coverage for class="a b" versus class="a"; done means strict mode rejects subset matches while the current default behavior remains unchanged.