fix: Validate that all application names are valid domain names

Invalid application names will need to be manually cleaned up by the user, and as such this is a bc-break.

Closes #3054

tests/unit/10_apps.bats

@@ -25,7 +25,16 @@ teardown () {
   echo "output: "$output
   echo "status: "$status
   assert_success
-  dokku --force apps:destroy 1994testapp
+
+  run dokku apps:create testapp:latest
+  echo "output: "$output
+  echo "status: "$status
+  assert_failure
+
+  run dokku apps:create testApp:latest
+  echo "output: "$output
+  echo "status: "$status
+  assert_failure
 
   run dokku apps:create TestApp
   echo "output: "$output