nginx-aspnet-mysql: add dev envs configuration (#267)

* nginx-aspnet-mysql: add dev envs configuration
* Fix/enable MySQL/MariaDB health check
* Refactor `Dockerfile` for use as Compose app as well as with
  dev envs
* nginx-aspnet-mysql: remove DB healthcheck from dev envs config

Signed-off-by: Milas Bowman <milas.bowman@docker.com>

nginx-aspnet-mysql/compose.yaml

@@ -1,25 +1,25 @@
 services:
   backend:
-    build: backend
+    build:
+      context: backend
     restart: always
     secrets:
       - db-password
-    depends_on: 
-      - db
+    depends_on:
+      db:
+        condition: service_healthy
     environment:
       - ASPNETCORE_URLS=http://+:8000
-#    depends_on:
-#      db:
-#        condition: service_healthy
+
   db:
     # We use a mariadb image which supports both amd64 & arm64 architecture
-    image: mariadb:10.6.4-focal
+    image: mariadb:10-focal
     # If you really want to use MySQL, uncomment the following line
-    #image: mysql:8.0.27
+    #image: mysql:8
     command: '--default-authentication-plugin=mysql_native_password'
     restart: always
     healthcheck:
-      test: ["CMD", "mysqladmin", "ping", "-h", "127.0.0.1", "--silent"]
+      test: ['CMD-SHELL', 'mysqladmin ping -h 127.0.0.1 --password="$$(cat /run/secrets/db-password)" --silent']
       interval: 3s
       retries: 5
       start_period: 30s
@@ -37,8 +37,10 @@ services:
       - 80:80
     depends_on: 
       - backend
+
 volumes:
   db-data:
+
 secrets:
   db-password:
-    file: db/password.txt
+    file: db/password.txt