Allow setting a channel for new users to auto-join (#9291)

Release Notes:

- Automatically add new users to the #zed channel

crates/collab/k8s/collab.template.yml

@@ -185,6 +185,8 @@ spec:
               value: "true"
             - name: ZED_ENVIRONMENT
               value: ${ZED_ENVIRONMENT}
+            - name: AUTO_JOIN_CHANNEL_ID
+              value: ${AUTO_JOIN_CHANNEL_ID}
           securityContext:
             capabilities:
               # FIXME - Switch to the more restrictive `PERFMON` capability.

crates/collab/k8s/environments/production.sh

@@ -1,4 +1,5 @@
 ZED_ENVIRONMENT=production
 RUST_LOG=info
 INVITE_LINK_PREFIX=https://zed.dev/invites/
+AUTO_JOIN_CHANNEL_ID=283
 DATABASE_MAX_CONNECTIONS=85

crates/collab/k8s/environments/staging.sh

@@ -2,3 +2,4 @@ ZED_ENVIRONMENT=staging
 RUST_LOG=info
 INVITE_LINK_PREFIX=https://staging.zed.dev/invites/
 DATABASE_MAX_CONNECTIONS=5
+AUTO_JOIN_CHANNEL_ID=8