feat(config): add option to specify default value to env var expansion (#5020)

* feat: Add option to specify default value to env var expansion

* fix: remove unused capturing group for env var replacement

Co-authored-by: Nicolas Giard <github@ngpixel.com>

dev/build/config.yml

@@ -15,6 +15,6 @@ ssl:
   provider: letsencrypt
   domain: $(LETSENCRYPT_DOMAIN)
   subscriberEmail: $(LETSENCRYPT_EMAIL)
-logLevel: info
-logFormat: $(LOG_FORMAT)
+logLevel: $(LOG_LEVEL:info)
+logFormat: $(LOG_FORMAT:default)
 ha: $(HA_ACTIVE)