Explicitly use PUBLIC schema

Also include that schema in all tests (otherwise they fail).  But it _does_ assume users will
install with that schema visible.

ddl/000011_parade.up.sql

@@ -1,6 +1,6 @@
 BEGIN;
 
-CREATE EXTENSION IF NOT EXISTS pgcrypto SCHEMA public;
+CREATE EXTENSION IF NOT EXISTS pgcrypto SCHEMA public CASCADE;
 
 CREATE TYPE task_status_code_value AS ENUM (
     'pending',          -- waiting for an actor to perform it (new or being retried)

testutil/db.go

@@ -128,7 +128,7 @@ func GetDB(t testing.TB, uri string, opts ...GetDBOption) (db.Database, string)
 		strings.ReplaceAll(uuid.New().String(), "-", ""))
 
 	// create connection
-	connURI := fmt.Sprintf("%s&search_path=%s", uri, generatedSchema)
+	connURI := fmt.Sprintf("%s&search_path=%s,public", uri, generatedSchema)
 	pool, err := pgxpool.Connect(ctx, connURI)
 	if err != nil {
 		t.Fatalf("could not connect to PostgreSQL: %s", err)