Function getRelationshipFromField

getRelationshipFromField(fieldWithRelationship): [relationshipId: string, attribute: string] | [relationshipId: undefined, attribute: undefined]
Retrieves the relationship id and attribute from the given field string if a relationship exists.
Parameters
- fieldWithRelationship: string
  The field string that possibly contains the relationship.
Returns [relationshipId: string, attribute: string] | [relationshipId: undefined, attribute: undefined]
The id of the relationship and the attribute or undefined for both if one can't be found.