collab: Setup database for LLM service (#15882)

This PR puts the initial infrastructure for the LLM service's database
in place.

The LLM service will be using a separate Postgres database, with its own
set of migrations.

Currently we only connect to the database in development, as we don't
yet have the database setup for the staging/production environments.

Release Notes:

- N/A

script/sqlx

@@ -1,17 +0,0 @@
-#!/bin/bash
-
-set -e
-
-# Install sqlx-cli if needed
-if [[ "$(sqlx --version)" != "sqlx-cli 0.5.7" ]]; then
-    echo "sqlx-cli not found or not the required version, installing version 0.5.7..."
-    cargo install sqlx-cli --version 0.5.7
-fi
-
-cd crates/collab
-
-# Export contents of .env.toml
-eval "$(cargo run --bin dotenv)"
-
-# Run sqlx command
-sqlx $@