Data Access: Add fields for Vendor User to Community and ServiceTicket schemas

[nnoce14]

On the Community schema, we want to add a new field called approvedVendors on the root of the schema.
This field will be typed as an array of VendorUser records. Refer to the ApplicantUser schema definition in AHP project for a reference on how to implement this type of field. It's not something Mongoose support directly but we were able to get it working in AHP.

On the ServiceTicket schema, add a new field called assignedVendor which is a reference field for the VendorUser type.

Make the necessary changes for the new fields to the domain context files, domain adapters, graphql types, and application services as well.