This is breaking change where bigint and bigserial Postgres types will be encoded as GraphQL String types, as opposed to Int as present in earlier releases.
Input types were already encoded as String.
This is achieved by selecting `bigint` and `bigserial` columns as `text`s in the SQL query: `select "big_id"::text ..` instead of `select "big_id" .. `.
Reason for that change is outlined in #633 where JavaScript cannot decode 64 bit Integers.
Insert trigger function: If query affects no rows then return `null`
Insert trigger function is modified to have
`IF r IS NULL THEN RETURN null; ELSE RETURN r; END IF;` in return statement.
### Description
What component does this PR affect?
- [x] Server
### Related Issue
#494
### Solution and Design
Use `quote_ident()` SQL function over `constraint_name` in insert trigger function definition.
### Type
- [x] Bug fix (non-breaking change which fixes an issue)
