Add gRPC fields to client api and agent check endpoint docs

api/agent.go

@@ -97,6 +97,8 @@ type AgentServiceCheck struct {
 	Status            string              `json:",omitempty"`
 	Notes             string              `json:",omitempty"`
 	TLSSkipVerify     bool                `json:",omitempty"`
+	GRPC              string              `json:",omitempty"`
+	GRPCUseTLS        bool                `json:",omitempty"`
 
 	// In Consul 0.7 and later, checks that are associated with a service
 	// may also contain this optional DeregisterCriticalServiceAfter field,

website/source/api/agent/check.html.md

@@ -121,6 +121,15 @@ The table below shows this endpoint's support for
   container using the specified `Shell`. Note that `Shell` is currently only
   supported for Docker checks.
 
+- `GRPC` `(string: "")` - Specifies a `gRPC` check's endpoint that supports the standard
+  [gRPC health checking protocol](https://github.com/grpc/grpc/blob/master/doc/health-checking.md).
+  The state of the check will be updated at the given `Interval` by probing the configured
+  endpoint.
+
+- `GRPCUseTLS` `(bool: false)` - Specifies whether to use TLS for this `gRPC` health check.
+  If TLS is enabled, then by default, a valid TLS certificate is expected. Certificate
+  verification can be turned off by setting `TLSSkipVerify` to `true`.
+
 - `HTTP` `(string: "")` - Specifies an `HTTP` check to perform a `GET` request
   against the value of `HTTP` (expected to be a URL) every `Interval`. If the
   response is any `2xx` code, the check is `passing`. If the response is `429
@@ -135,6 +144,10 @@ The table below shows this endpoint's support for
 - `Header` `(map[string][]string: {})` - Specifies a set of headers that should
   be set for `HTTP` checks. Each header can have multiple values.
 
+- `Timeout` `(duration: 10s)` - Specifies a timeout for outgoing connections in the
+  case of a Script, HTTP, TCP, or gRPC check. Can be specified in the form of "10s"
+  or "5m" (i.e., 10 seconds or 5 minutes, respectively).
+
 - `TLSSkipVerify` `(bool: false)` - Specifies if the certificate for an HTTPS
   check should not be verified.