Allow overriding TRUSTED_HOSTS and MERCURE_PUBLIC_URL variables (#2666)

* build(compose.yaml): allow overriding TRUSTED_HOSTS and MERCURE_PUBLIC_URL variables

Fix issue with invalid TRUSTED_HOSTS and MERCURE_PUBLIC_URL when using http://localhost or :80 as SERVER_NAME

* Apply suggestions from code review

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Co-authored-by: JH <je.hu@pm.me>
Co-authored-by: Vincent <407859+vincentchalamon@users.noreply.github.com>

compose.yaml

@@ -10,10 +10,10 @@ services:
       MERCURE_PUBLISHER_JWT_KEY: ${CADDY_MERCURE_JWT_SECRET:-!ChangeThisMercureHubJWTSecretKey!}
       MERCURE_SUBSCRIBER_JWT_KEY: ${CADDY_MERCURE_JWT_SECRET:-!ChangeThisMercureHubJWTSecretKey!}
       TRUSTED_PROXIES: ${TRUSTED_PROXIES:-127.0.0.0/8,10.0.0.0/8,172.16.0.0/12,192.168.0.0/16}
-      TRUSTED_HOSTS: ^${SERVER_NAME:-example\.com|localhost}|php$$
+      TRUSTED_HOSTS: ${TRUSTED_HOSTS:-^${SERVER_NAME:-example\.com|localhost}|php$$}
       DATABASE_URL: postgresql://${POSTGRES_USER:-app}:${POSTGRES_PASSWORD:-!ChangeMe!}@database:5432/${POSTGRES_DB:-app}?serverVersion=${POSTGRES_VERSION:-16}&charset=${POSTGRES_CHARSET:-utf8}
       MERCURE_URL: ${CADDY_MERCURE_URL:-http://php/.well-known/mercure}
-      MERCURE_PUBLIC_URL: https://${SERVER_NAME:-localhost}/.well-known/mercure
+      MERCURE_PUBLIC_URL: ${CADDY_MERCURE_PUBLIC_URL:-https://${SERVER_NAME:-localhost}/.well-known/mercure}
       MERCURE_JWT_SECRET: ${CADDY_MERCURE_JWT_SECRET:-!ChangeThisMercureHubJWTSecretKey!}
     volumes:
       - caddy_data:/data