WIP transactions, savepoints and connection pooling

[cirospaciari]

What does this PR do?

• Documentation or TypeScript types (it's okay to leave the rest blank in this case)
• Code changes

Add support for transactions:

BEGIN / COMMIT await sql.begin([options = ''], fn) -> fn()

import { SQL } from "bun:sql";

const sql = new SQL({
  host: "localhost",
  port: 5432,
  user: "ciro",
  password: "bunbunbun",
  database: "bun",
});

const [user, account] = await sql.begin(async sql => {
  const [user] = await sql`
    insert into users (
      name
    ) values (
      'Murray'
    )
    returning *
  `

  const [account] = await sql`
    insert into accounts (
      user_id
    ) values (
      ${ user.user_id }
    )
    returning *
  `

  return [user, account]
})

SAVEPOINT await sql.savepoint([name], fn) -> fn()

sql.begin('read write', async sql => {
  const [user] = await sql`
    insert into users (
      name
    ) values (
      'Murray'
    )
  `

  const [account] = (await sql.savepoint(sql =>
    sql`
      insert into accounts (
        user_id
      ) values (
        ${ user.user_id }
      )
    `
  ).catch(err => {
    // Account could not be created. ROLLBACK SAVEPOINT is called because we caught the rejection.
  })) || []

  return [user, account]
})
.then(([user, account]) => {
  // great success - COMMIT succeeded
})
.catch(() => {
  // not so good - ROLLBACK was called
})

How did you verify your code works?

[robobun]

^{Updated 12:42 PM PT - Jan 13th, 2025}

✅ @cirospaciari, your commit 25eeff3 has passed in #9515! 🎉

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🧪   try this PR locally:

bunx bun-pr 16320