Run SQLx migrations on startup

migrations/20240101000001_create_user_settings.sql

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+-- Create user_settings table
+CREATE TABLE IF NOT EXISTS user_settings (
+    id SERIAL PRIMARY KEY,
+    user_id BIGINT NOT NULL UNIQUE,
+    last_name VARCHAR(64) NOT NULL,
+    first_name VARCHAR(64) NOT NULL,
+    username VARCHAR(32) NOT NULL,
+    source VARCHAR(32) NOT NULL
+);
+
+-- Create unique index on user_id (if not exists from UNIQUE constraint)
+CREATE UNIQUE INDEX IF NOT EXISTS user_settings_user_id_key ON user_settings(user_id);