Add support for nested conditions in $filter

[Sjustein]

Building upon the implementation of the AST in #5 , add support for brackets and nesting statements. The odata specification does support nesting and it has benefits for more advanced use cases. The output datatypes should be updated to properly reflect the parsed result.

Acceptance criteria

• Implement an AST to support or conditions in $filter #5 is used as a basis for this implementation.
• The AST parses brackets and succesfully outputs a custom datatype reflection of the nested statements.
• Tests are written to properly test the nesting implementation and the pipeline passes.