Natural query parser for evitaQL (prototype)

Prototype of a natural version of evitaQL language used by evitaDB. This project was created as a way to explore ANTLR4 capabilities.

It converts following grammar

gimme
	page of 1 and 20
	and also
	facet summary with 'COUNTS'
	and also
	entities with
		attribute of 'code' and 'name'
from collection of 'product'
such that
	attribute 'code' equals to 'macbook'
	otherwise
	attribute 'name' starts with 'Mac'
	and also
	price is in price list 'vip' and 'basic'
in order of
	price in ascending natural order
	and also
	attribute 'code' in descending natural order

into the original evitaDB's evitaQL language

query(
    collection("product"),
    filterBy(
        and(
            or(
                attributeEquals("code", "macbook"),
                attributeStartsWith("name", "Mac")
            ),
            priceInPriceLists("vip", "basic")
        )
    ),
    orderBy(
        priceNatural(),
        attributeNatural("code", OrderDirection.DESC)
    ),
    require(
        page(1, 20),
        facetSummary(),
        entityFetch(
            attributeContent("code", "name")
        )
    )
)

It can be seen in action in io.evitadb.api.query.natural.parser.ParserTest.