Bootstrap a Consul Datacenter

This is the hands-on lab for Section 3 of the Consul 101 course. You start with three bare Ubuntu servers that have Consul installed but not configured, and you bring up a healthy three-server datacenter with your own hands, exactly the way Section 3's lessons describe.

You will:

• Generate a gossip encryption key with `consul keygen` and apply it identically on every server
• Author a single server configuration with `bootstrap_expect = 3`, a `retry_join` list, and go-sockaddr address templates, then distribute it to all three servers
• Start Consul and watch the servers wait for the full set ("expecting 3 servers") before a real leader election runs
• Confirm gossip encryption is on and consistent across the whole pool, and see what a mismatched key does to a node
• Fail a server with `systemctl stop`, watch it stay in the Raft peer set (server defaults protect quorum), rejoin it via `retry_join`, then gracefully remove it with `consul leave`

By the end you will have bootstrapped a real Consul quorum and exercised the join, rejoin, and leave behaviors that decide whether a cluster stays healthy.