feat: modify config-ssh to set the host suffix (coder#17280)

Wires up `config-ssh` command to use a hostname suffix if configured.

part of: coder#16828


e.g. `coder config-ssh --hostname-suffix spiketest` gives:

```
# ------------START-CODER-----------
# This section is managed by coder. DO NOT EDIT.
#
# You should not hand-edit this section unless you are removing it, all
# changes will be lost when running "coder config-ssh".
#
# Last config-ssh options:
# :hostname-suffix=spiketest
#
Host coder.* *.spiketest
        ConnectTimeout=0
        StrictHostKeyChecking=no
        UserKnownHostsFile=/dev/null
        LogLevel ERROR
        ProxyCommand /home/coder/repos/coder/build/coder_config_ssh --global-config /home/coder/.config/coderv2 ssh --stdio --ssh-host-prefix coder. --hostname-suffix spiketest %h
# ------------END-CODER------------
```

Author: spikecurtis

cli/configssh.go

@@ -356,9 +356,15 @@ func (r *RootCmd) configSSH() *serpent.Command {
 				if sshConfigOpts.disableAutostart {
 					flags += " --disable-autostart=true"
 				}
+				if coderdConfig.HostnamePrefix != "" {
+					flags += " --ssh-host-prefix " + coderdConfig.HostnamePrefix
+				}
+				if coderdConfig.HostnameSuffix != "" {
+					flags += " --hostname-suffix " + coderdConfig.HostnameSuffix
+				}
 				defaultOptions = append(defaultOptions, fmt.Sprintf(
-					"ProxyCommand %s %s ssh --stdio%s --ssh-host-prefix %s %%h",
-					escapedCoderBinary, rootFlags, flags, coderdConfig.HostnamePrefix,
+					"ProxyCommand %s %s ssh --stdio%s %%h",
+					escapedCoderBinary, rootFlags, flags,
 				))
 			}
 
@@ -391,7 +397,7 @@ func (r *RootCmd) configSSH() *serpent.Command {
 			}
 
 			hostBlock := []string{
-				"Host " + coderdConfig.HostnamePrefix + "*",
+				sshConfigHostLinePatterns(coderdConfig),
 			}
 			// Prefix with '\t'
 			for _, v := range configOptions.sshOptions {
@@ -837,3 +843,19 @@ func diffBytes(name string, b1, b2 []byte, color bool) ([]byte, error) {
 	}
 	return b, nil
 }
+
+func sshConfigHostLinePatterns(config codersdk.SSHConfigResponse) string {
+	builder := strings.Builder{}
+	// by inspection, WriteString always returns nil error
+	_, _ = builder.WriteString("Host")
+	if config.HostnamePrefix != "" {
+		_, _ = builder.WriteString(" ")
+		_, _ = builder.WriteString(config.HostnamePrefix)
+		_, _ = builder.WriteString("*")
+	}
+	if config.HostnameSuffix != "" {
+		_, _ = builder.WriteString(" *.")
+		_, _ = builder.WriteString(config.HostnameSuffix)
+	}
+	return builder.String()
+}

cli/configssh_test.go

@@ -611,6 +611,33 @@ func TestConfigSSH_FileWriteAndOptionsFlow(t *testing.T) {
 				regexMatch: "RemoteForward 2222 192.168.11.1:2222.*\n.*RemoteForward 2223 192.168.11.1:2223",
 			},
 		},
+		{
+			name: "Hostname Suffix",
+			args: []string{
+				"--yes",
+				"--hostname-suffix", "testy",
+			},
+			wantErr:  false,
+			hasAgent: true,
+			wantConfig: wantConfig{
+				ssh:        []string{"Host coder.* *.testy"},
+				regexMatch: `ProxyCommand .* ssh .* --hostname-suffix testy %h`,
+			},
+		},
+		{
+			name: "Hostname Prefix and Suffix",
+			args: []string{
+				"--yes",
+				"--ssh-host-prefix", "presto.",
+				"--hostname-suffix", "testy",
+			},
+			wantErr:  false,
+			hasAgent: true,
+			wantConfig: wantConfig{
+				ssh:        []string{"Host presto.* *.testy"},
+				regexMatch: `ProxyCommand .* ssh .* --ssh-host-prefix presto\. --hostname-suffix testy %h`,
+			},
+		},
 	}
 	for _, tt := range tests {
 		tt := tt