TypeORM Upsert

Say you have a TypeORM entity Post and you want to atomically upsert:

``typescript
import { Upsert } from 'typeorm-upsert'
import { SnakeCase } from 'snake-case'


const post: Post = { ... }

(async () => {
const upserted_post = await Upsert(
Post,
post,
"id", // primary-key to upsert on

// optional params
{
key_naming_transform: SnakeCase, // arbitrarily transform keys before UPSERT
do_not_upsert: ['created_at'] // exclude non-nullable keys from UPDATE that are required in the event of an INSERT operation
}
)

console.log(upserted_post) // prints the finished version of Post
})
``

Tested with PostgreSQL 9.5+. Contributors welcome.