fix(schematypes): add property "defaultOptions"

[hasezoey]

Summary

This PR adds the property defaultOptions for SchemaType and its extending classes
for SchemaType itself, property defaultOptions is optional, see: (and also search through the file, there is no explicit assignment)

mongoose/lib/schematype.js

Line 55 in 5528a64

const defaultOptions = this.constructor.defaultOptions || {};

but all mongoose provided extending classes explicitly define it:

mongoose/lib/schema/SubdocumentPath.js

Line 326 in 5528a64

SubdocumentPath.defaultOptions = {};

[AbdelrahmanHafez]

LGTM, thanks! 👍

[vkarpov15]

Thanks 👍