Allow functions to be defined as the defaultValue, to return a scalar value

[MrSwitch]

In order to generate random numbers, hashes etc, as well as allow values to be derived from another value allow the defaultValue property to be a handler function which takes the current operation and assigns a value to it.

i.e...

// Member
const member = {
	schema: {
		name: {
			[method]: { // i.e. 'post'
				defaultValue(item) {
					return `${item.firstName} ${item.lastName}`;
				}
			}
		}
	}
};

const dare = new Dare({models: {member}});

// Post
await dare.post('member', {
	firstName: 'Andrew',
	lastName: 'Dodson',
});

// # Generates the query...
// INSERT INTO member (firstName, lastName, name)
// VALUES ('Andrew', 'Dodson', 'Andrew Dodson');