Add documentation for network tier (hashicorp#1593)

* Add documentation for network tier

* Add named links to fwd rule docs

* add documentation for network address

* Fix typo

Author: rosbo

docs/r/compute_address.html.markdown

@@ -51,6 +51,10 @@ The following arguments are supported:
     specified for INTERNAL address types. The IP address must be inside the
     specified subnetwork, if any.
 
+* `network_tier` - (Optional) The [networking tier][network-tier] used for configuring
+    this address. This field can take the following values: PREMIUM or STANDARD.
+    If this field is not specified, it is assumed to be PREMIUM.
+
 ## Attributes Reference
 
 In addition to the arguments listed above, the following computed attributes are
@@ -86,3 +90,5 @@ $ terraform import google_compute_address.default https://www.googleapis.com/com
 
 $ terraform import google_compute_address.default projects/gcp-project/regions/us-central1/addresses/test-address
 ```
+
+[network-tier]: https://cloud.google.com/network-tiers/docs/overview

docs/r/compute_forwarding_rule.html.markdown

@@ -51,6 +51,10 @@ The following arguments are supported:
     should belong to. Only used for internal load balancing. If it is not
     provided, the default network is used.
 
+* `network_tier` - (Optional) The [networking tier][network-tier] used for configuring
+    this forwarding rule. This field can take the following values: PREMIUM or STANDARD.
+    If this field is not specified, it is assumed to be PREMIUM.
+
 * `port_range` - (Optional) A range e.g. "1024-2048" or a single port "1024"
     (defaults to all ports!). Only used for external load balancing.
   Some types of forwarding targets have constraints on the acceptable ports:
@@ -91,3 +95,5 @@ Forwarding rules can be imported using the `name`, e.g.
 ```
 $ terraform import google_compute_forwarding_rule.default website-forwarding-rule
 ```
+
+[network-tier]: https://cloud.google.com/network-tiers/docs/overview

docs/r/compute_instance.html.markdown

@@ -227,6 +227,10 @@ The `access_config` block supports:
     See [the docs](https://cloud.google.com/compute/docs/instances/create-ptr-record) for how
     to become verified as a domain owner.
 
+* `network_tier` - (Optional) The [networking tier][network-tier] used for configuring this instance.
+    This field can take the following values: PREMIUM or STANDARD. If this field is
+    not specified, it is assumed to be PREMIUM.
+
 The `alias_ip_range` block supports:
 
 * `ip_cidr_range` - The IP CIDR range represented by this alias IP range. This IP CIDR range
@@ -310,3 +314,4 @@ $ terraform import google_compute_instance.default gcp-project/us-central1-a/tes
 ```
 
 [custom-vm-types]: https://cloud.google.com/dataproc/docs/concepts/compute/custom-machine-types
+[network-tier]: https://cloud.google.com/network-tiers/docs/overview

docs/r/compute_instance_template.html.markdown

@@ -249,6 +249,10 @@ The `access_config` block supports:
 * `nat_ip` - (Optional) The IP address that will be 1:1 mapped to the instance's
     network ip. If not given, one will be generated.
 
+* `network_tier` - (Optional) The [networking tier][network-tier] used for configuring
+    this instance template. This field can take the following values: PREMIUM or
+    STANDARD. If this field is not specified, it is assumed to be PREMIUM.
+
 The `alias_ip_range` block supports:
 
 * `ip_cidr_range` - The IP CIDR range represented by this alias IP range. This IP CIDR range
@@ -312,3 +316,4 @@ $ terraform import google_compute_instance_template.default appserver-template
 ```
 
 [custom-vm-types]: https://cloud.google.com/dataproc/docs/concepts/compute/custom-machine-types
+[network-tier]: https://cloud.google.com/network-tiers/docs/overview