fix(postgres): escape identifier in createSchema and dropSchema (#15752)

Fixes #15651. This patch backports a part of #14999 to Sequelize v6 to
quote schema identifiers in PostgreSQL `createSchema()` and
`dropSchema()`.

src/dialects/postgres/query-generator.js

@@ -46,14 +46,14 @@ class PostgresQueryGenerator extends AbstractQueryGenerator {
     const databaseVersion = _.get(this, 'sequelize.options.databaseVersion', 0);
 
     if (databaseVersion && semver.gte(databaseVersion, '9.2.0')) {
-      return `CREATE SCHEMA IF NOT EXISTS ${schema};`;
+      return `CREATE SCHEMA IF NOT EXISTS ${this.quoteIdentifier(schema)};`;
     }
 
-    return `CREATE SCHEMA ${schema};`;
+    return `CREATE SCHEMA ${this.quoteIdentifier(schema)};`;
   }
 
   dropSchema(schema) {
-    return `DROP SCHEMA IF EXISTS ${schema} CASCADE;`;
+    return `DROP SCHEMA IF EXISTS ${this.quoteIdentifier(schema)} CASCADE;`;
   }
 
   showSchemasQuery() {

test/unit/sql/create-schema.test.js

@@ -10,7 +10,7 @@ describe(Support.getTestDialectTeaser('SQL'), () => {
     describe('dropSchema', () => {
       it('IF EXISTS', () => {
         expectsql(sql.dropSchema('foo'), {
-          postgres: 'DROP SCHEMA IF EXISTS foo CASCADE;'
+          postgres: 'DROP SCHEMA IF EXISTS "foo" CASCADE;'
         });
       });
     });
@@ -27,14 +27,14 @@ describe(Support.getTestDialectTeaser('SQL'), () => {
       it('9.2.0 or above', () => {
         current.options.databaseVersion = '9.2.0';
         expectsql(sql.createSchema('foo'), {
-          postgres: 'CREATE SCHEMA IF NOT EXISTS foo;'
+          postgres: 'CREATE SCHEMA IF NOT EXISTS "foo";'
         });
       });
 
       it('below 9.2.0', () => {
         current.options.databaseVersion = '9.0.0';
         expectsql(sql.createSchema('foo'), {
-          postgres: 'CREATE SCHEMA foo;'
+          postgres: 'CREATE SCHEMA "foo";'
         });
       });
     });