Condition could have more detailed fields

Currently, when I parse a query, I get WHERE as Condition instances. These have an expr field, which is just a string and not very useful when analyzing a query. It would be really nice if we could be able to get more detail from that, like the operator, operands, etc.

Examples:

// c.id = 2
[
    leftOperand: ColumnReference [ column: 'id', tableAlias: 'c' ] ,
    operator: Equals []
    rightOperand: Constant [ value: 2 ]
]

// customer.address_id IS NOT NULL
[
    leftOperand: ColumnReference [ column: 'address_id', tableName: 'customer' ] ,
    operator: IsNotNull
    rightOperand: null
]

Beginne damit, die Condition-Instanzen des Parsers und das vorhandene expr-Feld zu lokalisieren. Vergleiche die angeforderten Beispiele c.id = 2 und customer.address_id IS NOT NULL und definiere anschließend, welche strukturierten Informationen zu Operator und Operand offengelegt werden müssen; die Arbeit ist abgeschlossen, wenn conditions diese Details anstelle nur eines Strings bereitstellen.