Add generic types for Node#labels, Relationship#type and UnboundRelationship#type

[bigmontz]

This generic types enable defining a list string like values accepted for an specific node labels list or relationship type.

Node example:

type PersonLabels = 'Person' | 'Actor'

// get the person from a non-typed record. If the record is correctly type-mapped
// the Node type can be omitted since it will be inferred.
const person: Node<Integer, PersonProps, PersonLabels> = record.get('person')

// get labels
// the type inferred for the labels will be PersonLabels[]
const labels = person.labels

// @ts-exepct-error
const wrongLabels: 'Car'|'Bicycle'[] = person.labels

Relationship/UnboundRelationship example:

type ActedInType = 'ACTED_IN'

// get the relationship from a non-typed record. If the record is correctly type mapped
// the Relationship type can be omitted since it will be inferred.
const actedIn: Relationship<Integer, ActedInProps, ActedInType> = record.get('actedIn')

// get type
// the type inferred for the relType will be 'ACTED_IN'
const relType = actedIn.type

// @ts-expect-error
const directed: 'DIRECTED' = actedIn.type

⚠️ This type definitions are not asserted in runtime. Thus mismatched type records coming from the database will not trigger type errors.

[robsdedude]

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