fix: Only create users in mysql 8.0 if they don't already exist (#1112)

This issue was breaking provisioning early in the process.

The volumes for mysql57 and mysql80 may still contain users from previous
provisioning runs. The old provisioning script for mysql 5.7 (provision.sql)
uses implicit user creation via the `GRANT` statement, which is no longer
supported in mysql 8.0. Therefore, the `CREATE USER` statements in
provision-mysql80.sql fail. The fix here is to change to `CREATE USER IF
NOT EXISTS`.

I've also deleted `drop-mysql-user.sql`. I suspect it was only used during
testing to enable repeated tests of provisioning, but it's not referenced
anywhere in the PR that adds it (#1097).

Author: timmc-edx

Makefile

@@ -496,7 +496,8 @@ dev.reset: dev.remove-containers dev.reset-repos dev.prune dev.pull.large-and-sl
 dev.destroy.coursegraph: dev.remove-containers.coursegraph ## Remove all coursegraph data.
 	docker volume rm ${COMPOSE_PROJECT_NAME}_coursegraph_data
 
-dev.destroy: ## Irreversibly remove all devstack-related containers, networks, and volumes.
+# See https://github.com/openedx/devstack/issues/1113 for lack of ability to destroy data volumes
+dev.destroy: ## Irreversibly remove all devstack-related containers and networks (though not data volumes)
 	$(WINPTY) bash ./destroy.sh
 
 ########################################################################################

drop-mysql-user.sql

@@ -1,29 +1,33 @@
+-- The use of `CREATE USER IF NOT EXISTS` is necessary since the
+-- mysql80_data volume may already contain these users due to previous
+-- provisioning https://github.com/openedx/devstack/issues/1113
+
 CREATE DATABASE IF NOT EXISTS credentials;
-CREATE USER 'credentials001'@'%' IDENTIFIED BY 'password';
+CREATE USER IF NOT EXISTS 'credentials001'@'%' IDENTIFIED BY 'password';
 GRANT ALL ON credentials.* TO 'credentials001'@'%';
 
 CREATE DATABASE IF NOT EXISTS discovery;
-CREATE USER 'discov001'@'%' IDENTIFIED BY 'password';
+CREATE USER IF NOT EXISTS 'discov001'@'%' IDENTIFIED BY 'password';
 GRANT ALL ON discovery.* TO 'discov001'@'%';
 
 CREATE DATABASE IF NOT EXISTS ecommerce;
-CREATE USER 'ecomm001'@'%' IDENTIFIED BY 'password';
+CREATE USER IF NOT EXISTS 'ecomm001'@'%' IDENTIFIED BY 'password';
 GRANT ALL ON ecommerce.* TO 'ecomm001'@'%';
 
 CREATE DATABASE IF NOT EXISTS notes;
-CREATE USER 'notes001'@'%' IDENTIFIED BY 'password';
+CREATE USER IF NOT EXISTS 'notes001'@'%' IDENTIFIED BY 'password';
 GRANT ALL ON notes.* TO 'notes001'@'%';
 
 CREATE DATABASE IF NOT EXISTS registrar;
-CREATE USER 'registrar001'@'%' IDENTIFIED BY 'password';
+CREATE USER IF NOT EXISTS 'registrar001'@'%' IDENTIFIED BY 'password';
 GRANT ALL ON registrar.* TO 'registrar001'@'%';
 
 CREATE DATABASE IF NOT EXISTS xqueue;
-CREATE USER 'xqueue001'@'%' IDENTIFIED BY 'password';
+CREATE USER IF NOT EXISTS 'xqueue001'@'%' IDENTIFIED BY 'password';
 GRANT ALL ON xqueue.* TO 'xqueue001'@'%';
 
 CREATE DATABASE IF NOT EXISTS `dashboard`;
-CREATE USER 'analytics001'@'%' IDENTIFIED BY 'password';
+CREATE USER IF NOT EXISTS 'analytics001'@'%' IDENTIFIED BY 'password';
 GRANT ALL ON `dashboard`.* TO 'analytics001'@'%';
 
 CREATE DATABASE IF NOT EXISTS `analytics-api`;
@@ -37,7 +41,7 @@ GRANT ALL ON `reports_v1`.* TO 'analytics001'@'%';
 
 CREATE DATABASE IF NOT EXISTS edxapp;
 CREATE DATABASE IF NOT EXISTS edxapp_csmh;
-CREATE USER 'edxapp001'@'%' IDENTIFIED BY 'password';
+CREATE USER IF NOT EXISTS 'edxapp001'@'%' IDENTIFIED BY 'password';
 GRANT ALL ON edxapp.* TO 'edxapp001'@'%';
 GRANT ALL ON edxapp_csmh.* TO 'edxapp001'@'%';