chore(CI): upgrade to MySQL 8 for CircleCI

Because:
 - we want to upgrade to MySQL 8

This commit:
 - use MySQL 8 on CircleCI

.circleci/config.yml

@@ -12,7 +12,8 @@ executors:
       - image: redis
       - image: memcached
       - image: pafortin/goaws
-      - image: cimg/mysql:5.7
+      - image: cimg/mysql:8.0.28
+        command: --default-authentication-plugin=mysql_native_password
       - image: jdlk7/firestore-emulator
         environment:
           NODE_ENV: dev
@@ -96,7 +97,8 @@ jobs:
       - image: redis
       - image: memcached
       - image: pafortin/goaws
-      - image: cimg/mysql:5.7
+      - image: cimg/mysql:8.0.28
+        command: --default-authentication-plugin=mysql_native_password
       - image: jdlk7/firestore-emulator
     environment:
       NODE_ENV: dev
@@ -119,7 +121,8 @@ jobs:
     resource_class: medium+
     docker:
       - image: cimg/node:16.13
-      - image: cimg/mysql:5.7
+      - image: cimg/mysql:8.0.28
+        command: --default-authentication-plugin=mysql_native_password
       - image: jdlk7/firestore-emulator
       - image: memcached
       - image: redis
@@ -260,7 +263,8 @@ jobs:
       - image: mcr.microsoft.com/playwright:v1.20.0-focal
       - image: redis
       - image: memcached
-      - image: cimg/mysql:5.7
+      - image: cimg/mysql:8.0.28
+        command: --default-authentication-plugin=mysql_native_password
       - image: jdlk7/firestore-emulator
     environment:
       NODE_ENV: dev

packages/fxa-auth-server/test/oauth/db/index.js

@@ -87,7 +87,12 @@ describe('db', function () {
     it('should use utf8', function () {
       return db.getEncodingInfo().then(function (info) {
         assert.equal(info['character_set_connection'], 'utf8mb4');
-        assert.equal(info['character_set_database'], 'utf8');
+
+        // When our databases are created by mysql-patcher, 'utf8' is specificed
+        // for the character set.  'utf8' is an alias for 'utf8mb3'.  See
+        // https://dev.mysql.com/doc/refman/8.0/en/charset-unicode-utf8.html
+        assert.equal(info['character_set_database'], 'utf8mb3');
+
         assert.equal(info['collation_connection'], 'utf8mb4_unicode_ci');
         assert.equal(info['collation_database'], 'utf8_unicode_ci');
       });