It's can't start caddy service when upgrade from 3.18.3 to 4.1.2

Description:

I upgrade from 3.18.1 to 4.1.2 use snap.But it’s will can’t start caddy.
Error message:
2021-12-02T21:41:29+08:00 systemd[1]: Started Service for snap application rocketchat-server.rocketchat-caddy. 2021-12-02T21:41:29+08:00 rocketchat-server.rocketchat-caddy[2351]: {“level”:“info”,“ts”:1638452489.7481782,“msg”:“using provided configuration”,“config_file”:"/var/snap/rocketchat-server/1494/Caddyfile",“config_adapter”:""} 2021-12-02T21:41:29+08:00 rocketchat-server.rocketchat-caddy[2351]: run: adapting config using caddyfile: /var/snap/rocketchat-server/1494/Caddyfile:2: unrecognized directive: proxy 2021-12-02T21:41:29+08:00 systemd[1]: snap.rocketchat-server.rocketchat-caddy.service: Main process exited, code=exited, status=1/FAILURE 2021-12-02T21:41:29+08:00 systemd[1]: snap.rocketchat-server.rocketchat-caddy.service: Failed with result ‘exit-code’. 2021-12-02T21:41:29+08:00 systemd[1]: snap.rocketchat-server.rocketchat-caddy.service: Scheduled restart job, restart counter is at 5. 2021-12-02T21:41:29+08:00 systemd[1]: Stopped Service for snap application rocketchat-server.rocketchat-caddy. 2021-12-02T21:41:29+08:00 systemd[1]: snap.rocketchat-server.rocketchat-caddy.service: Start request repeated too quickly. 2021-12-02T21:41:29+08:00 systemd[1]: snap.rocketchat-server.rocketchat-caddy.service: Failed with result ‘exit-code’. 2021-12-02T21:41:29+08:00 systemd[1]: Failed to start Service for snap application rocketchat-server.rocketchat-caddy.

Steps to reproduce:

1. run this command to switch snap channel: snap switch rocketchat-server --channel=4.x/edge
2. then run snap refresh rocketchat-server this command to upgrade and it's done.
3. Then see caddy service can't start.

Expected behavior:

It's should all service started.

Actual behavior:

Server Setup Information:

• Version of Rocket.Chat Server: 3.18.3 to 4.1.2
• Operating System: Ubuntu 20.04
• Deployment Method: snap
• Number of Running Instances: 1
• DB Replicaset Oplog:
• NodeJS Version: 12.22.1
• MongoDB Version: 3.6.14

Client Setup Information

• Desktop App or Browser Version: 3.6.0
• Operating System: Win10

Additional context

Relevant logs:

2021-12-02T21:41:29+08:00 systemd[1]: Started Service for snap application rocketchat-server.rocketchat-caddy.
2021-12-02T21:41:29+08:00 rocketchat-server.rocketchat-caddy[2351]: {“level”:“info”,“ts”:1638452489.7481782,“msg”:“using provided configuration”,“config_file”:"/var/snap/rocketchat-server/1494/Caddyfile",“config_adapter”:""}
2021-12-02T21:41:29+08:00 rocketchat-server.rocketchat-caddy[2351]: run: adapting config using caddyfile: /var/snap/rocketchat-server/1494/Caddyfile:2: unrecognized directive: proxy
2021-12-02T21:41:29+08:00 systemd[1]: snap.rocketchat-server.rocketchat-caddy.service: Main process exited, code=exited, status=1/FAILURE
2021-12-02T21:41:29+08:00 systemd[1]: snap.rocketchat-server.rocketchat-caddy.service: Failed with result ‘exit-code’.
2021-12-02T21:41:29+08:00 systemd[1]: snap.rocketchat-server.rocketchat-caddy.service: Scheduled restart job, restart counter is at 5.
2021-12-02T21:41:29+08:00 systemd[1]: Stopped Service for snap application rocketchat-server.rocketchat-caddy.
2021-12-02T21:41:29+08:00 systemd[1]: snap.rocketchat-server.rocketchat-caddy.service: Start request repeated too quickly.
2021-12-02T21:41:29+08:00 systemd[1]: snap.rocketchat-server.rocketchat-caddy.service: Failed with result ‘exit-code’.
2021-12-02T21:41:29+08:00 systemd[1]: Failed to start Service for snap application rocketchat-server.rocketchat-caddy.

Start with the generated /var/snap/rocketchat-server/1494/Caddyfile and the snap upgrade commands in the reproduction steps. Compare the Caddy configuration and service behavior before and after refreshing from the 3.x to 4.x channel, focusing on the reported unrecognized proxy directive. Done means the caddy service starts successfully after the documented snap upgrade.