Add IAM support for storage bucket (hashicorp#822)

* Add IAM support for storage bucket
* Add documentation
* Test multiple roles

docs/r/storage_bucket_iam.html.markdown

@@ -0,0 +1,63 @@
+---
+layout: "google"
+page_title: "Google: google_storage_bucket_iam"
+sidebar_current: "docs-google-storage-bucket-iam"
+description: |-
+ Collection of resources to manage IAM policy for a Google storage bucket.
+---
+
+# IAM policy for Google storage bucket
+
+Two different resources help you manage your IAM policy for storage bucket. Each of these resources serves a different use case:
+
+* `google_storage_bucket_iam_binding`: Authoritative for a given role. Updates the IAM policy to grant a role to a list of members. Other roles within the IAM policy for the storage bucket are preserved.
+* `google_storage_bucket_iam_member`: Non-authoritative. Updates the IAM policy to grant a role to a new member. Other members for the role for the storage bucket are preserved.
+
+~> **Note:** `google_storage_bucket_iam_binding` resources **can be** used in conjunction with `google_storage_bucket_iam_member` resources **only if** they do not grant privilege to the same role.
+
+## google\_storage\_bucket\_iam\_binding
+
+```hcl
+resource "google_storage_bucket_iam_binding" "binding" {
+  bucket = "your-bucket-name"
+  role        = "roles/storage.objectViewer"
+
+  members = [
+    "user:[email protected]",
+  ]
+}
+```
+
+## google\_storage\_bucket\_iam\_member
+
+```hcl
+resource "google_storage_bucket_iam_member" "member" {
+  bucket = "your-bucket-name"
+  role        = "roles/storage.objectViewer"
+  member      = "user:[email protected]"
+}
+```
+
+## Argument Reference
+
+The following arguments are supported:
+
+* `bucket` - (Required) The name of the bucket it applies to.
+
+* `member/members` - (Required) Identities that will be granted the privilege in `role`.
+  Each entry can have one of the following values:
+  * **allUsers**: A special identifier that represents anyone who is on the internet; with or without a Google account.
+  * **allAuthenticatedUsers**: A special identifier that represents anyone who is authenticated with a Google account or a service account.
+  * **user:{emailid}**: An email address that represents a specific Google account. For example, [email protected] or [email protected].
+  * **serviceAccount:{emailid}**: An email address that represents a service account. For example, [email protected].
+  * **group:{emailid}**: An email address that represents a Google group. For example, [email protected].
+  * **domain:{domain}**: A Google Apps domain name that represents all the users of that domain. For example, google.com or example.com.
+
+* `role` - (Required) The role that should be applied.
+
+## Attributes Reference
+
+In addition to the arguments listed above, the following computed attributes are
+exported:
+
+* `etag` - (Computed) The etag of the storage bucket's IAM policy.

google.erb

@@ -434,6 +434,14 @@
       <a href="/docs/providers/google/r/storage_bucket_acl.html">google_storage_bucket_acl</a>
       </li>
 
+      <li<%= sidebar_current("docs-google-storage-bucket-iam") %>>
+      <a href="/docs/providers/google/r/storage_bucket_iam.html">google_storage_bucket_iam_binding</a>
+      </li>
+
+      <li<%= sidebar_current("docs-google-storage-bucket-iam") %>>
+      <a href="/docs/providers/google/r/storage_bucket_iam.html">google_storage_bucket_iam_member</a>
+      </li>
+
       <li<%= sidebar_current("docs-google-storage-bucket-object") %>>
       <a href="/docs/providers/google/r/storage_bucket_object.html">google_storage_bucket_object</a>
       </li>
@@ -451,7 +459,13 @@
         <a href="/docs/providers/google/r/google_kms_key_ring.html">google_kms_key_ring</a>
       </li>
       <li<%= sidebar_current("docs-google-kms-key-ring-iam") %>>
-        <a href="/docs/providers/google/r/google_kms_key_ring_iam.html">google_kms_key_ring_iam_*</a>
+        <a href="/docs/providers/google/r/google_kms_key_ring_iam.html">google_kms_key_ring_iam_binding</a>
+      </li>
+      <li<%= sidebar_current("docs-google-kms-key-ring-iam") %>>
+        <a href="/docs/providers/google/r/google_kms_key_ring_iam.html">google_kms_key_ring_iam_member</a>
+      </li>
+      <li<%= sidebar_current("docs-google-kms-key-ring-iam") %>>
+        <a href="/docs/providers/google/r/google_kms_key_ring_iam.html">google_kms_key_ring_iam_policy</a>
       </li>
       <li<%= sidebar_current("docs-google-kms-crypto-key-x") %>>
         <a href="/docs/providers/google/r/google_kms_crypto_key.html">google_kms_crypto_key</a>