Add some target fields and move some things around (#3879)

In preparation for putting proxy code in the api package this creates some necessary fields in the target output and it pre-moves credential parsing and proxy handshake code to their new places. This will make the diff for the actual proxy code move quite a bit smaller.

Co-authored-by: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>

internal/gen/controller.swagger.json

@@ -6433,6 +6433,18 @@
           "description": "Output only. The endpoint address that the worker will connect to, useful for setting TLS parameters.",
           "readOnly": true
         },
+        "endpoint_port": {
+          "type": "integer",
+          "format": "int64",
+          "description": "Output only. The endpoint port that will be connected to, either from a\nport directly on the target or from a service definition.",
+          "readOnly": true
+        },
+        "expiration": {
+          "type": "string",
+          "format": "date-time",
+          "description": "Output only. The expiration time of the session.",
+          "readOnly": true
+        },
         "credentials": {
           "type": "array",
           "items": {