Support shorthand foreign key references

[nguyenalter]

Summary

• Support shorthand foreign key references syntax in PostgreSQL/MSSQL
• Fix: missing constraint names when importing from PostgreSQL/MSSQL foreign keys to DBML's refs

Issue

• https://community.dbdiagram.io/t/feature-request-add-foreign-key-constraints-support-to-dbml-conversion-from-sql-file/1454/5

Lasting Changes (Technical)

• Update setFields method in Endpoint class
• Add constraint names to DBML's refs
• Update testcases

Checklist

Please check directly on the box once each of these are done

• [ ] Documentation (if necessary)
• [x] Tests (integration test/unit test)
• [ ] Integration Tests Passed
• [ ] Code Review