relation to allow batch creation in 3.x

[davidcheung]

Bug or feature request

• Bug
• Feature request

Description of feature (or steps to reproduce if bug)

#2879 it didnt handle batchCreate for relations,
so in a scenario where POST /book/:id/page it will not inherit allowArray flag and therefore will not allowArray in 3.x's more strict coercion

related code

loopback/lib/model.js

Lines 499 to 506 in 6b6ca95

	define('__create__' + relationName, {
	isStatic: false,
	http: { verb: 'post', path: '/' + pathName },
	accepts: { arg: 'data', type: 'object', model: toModelName, http: { source: 'body' }},
	description: format('Creates a new instance in %s of this model.', relationName),
	accessType: 'WRITE',
	returns: { arg: 'data', type: toModelName, root: true },
	});

cc @bajtos

Update 18/11/16:

• @pthieu and @strongloop/squad-epitome needs to review add allowArray to relations' 'create' remoteMethod #2947, and Update sdk to use loopback 3.x loopback-sdk-angular#253 is blocked by this issue.

Update 22/11/16:

• Functionality was changed from last week, needs review.

Update 23/11/16:

• Still needs review.