fix(schema): Database connection not cleanly closed

This commit introduces closing the Schema Manager's underlying driver
connection. We were only releasing the shared lock but not actually
cleaning up the db connection and relied on the fact that the process
would exit to do that for us.

internal/db/schema/internal/postgres/postgres.go

@@ -251,6 +251,11 @@ func (p *Postgres) Run(ctx context.Context, migration io.Reader, version int, ed
 	return nil
 }
 
+// Close closes the underlying Postgres database connection.
+func (p *Postgres) Close() error {
+	return p.conn.Close()
+}
+
 var errOldMigrationTable = stderrors.New("old schema migration table")
 
 func (p *Postgres) schemaInitialized(ctx context.Context) (bool, error) {

internal/db/schema/manager.go

@@ -22,6 +22,7 @@ type driver interface {
 	Lock(context.Context) error
 	Unlock(context.Context) error
 	UnlockShared(context.Context) error
+	Close() error
 	// StartRun begins a transaction internal to the driver.
 	StartRun(context.Context) error
 	// CommitRun commits a transaction, if there is an error it should rollback the transaction.
@@ -123,6 +124,18 @@ func (b *Manager) CurrentState(ctx context.Context) (*State, error) {
 	return &dbS, nil
 }
 
+// Close unlocks the database shared lock and closes the underlying
+// database connection afterwards.
+func (b *Manager) Close(ctx context.Context) error {
+	const op = "schema.(Manager).Close"
+	err := b.SharedUnlock(ctx)
+	if err != nil {
+		return errors.Wrap(ctx, err, op)
+	}
+
+	return b.driver.Close()
+}
+
 // SharedLock attempts to obtain a shared lock on the database.  This can fail
 // if an exclusive lock is already held.  If the lock can't be obtained an
 // error is returned.