Switch over to using a variable for database name

Also addition to PostgreSQL role to drop any existing database with the same name to allow for playbook reruns.

roles/group_vars/all.sample

@@ -0,0 +1,4 @@
+# Specify the PostgreSQL database name you want to use for Mastodon
+# Please note that the playbook will drop this database in preparation for Mastodon's
+# database setup process.
+DB_NAME: 

roles/mastodon-config/templates/.env.production.sample

@@ -9,7 +9,7 @@ DB_HOST=/var/run/postgresql
 # Your PostgreSQL user
 DB_USER=mastodon
 # Your PostgreSQL DB name
-DB_NAME=mastodon_production
+DB_NAME={{ DB_NAME }}
 # Leave DB password empty
 DB_PASS=
 # Your DB_PORT

roles/mastodon-postgresql/tasks/main.yml

@@ -15,3 +15,9 @@
     state: present
   become: true
   become_user: postgres
+- name: Drop any existing database that may exist with the same name
+  postgresql_db:
+    name: {{ DB_NAME }}
+    state: absent
+    become: true
+    become_user: postgres