fix(dsg) admin ui added m2m relation

[abrl91]

fix #2225
we should delete #2354

On admin UI, added the ability to make a reference between two entities in a form of many to many (one to many from the entity perspective).
For example, an order can have many products and a product can be in many orders.

An order with its products

A product with its orders

To make it works I added the following block code on the edit entity and create entity files (post and tag for the example):

<ReferenceArrayInput
          source="tags"
          reference="Tag"
          parse={(value: any) => value && value.map((v: any) => ({ id: v }))}
          format={(value: any) => value && value.map((v: any) => v.id)}
        >
          <SelectArrayInput optionText={TagTitle} />
 </ReferenceArrayInput>

PR Checklist

• Tests for the changes have been added
• npm test doesn't throw any error

[yuval-hazaz]

@abrl91 great work!

[abrl91]

deploy to staging completed successfully 🔥