feat(invitation): add documentation for azuread_invitation resource

docs/resources/invitation.md

@@ -0,0 +1,65 @@
+---
+subcategory: "Invitations"
+---
+
+# Resource: azuread_invitation
+
+Manages an invitation of a guest user within Azure Active Directory.
+
+-> **NOTE:** If you're authenticating using a Service Principal then it must have permissions to `User.ReadWrite.All` within the `Microsoft Graph` API.
+
+## Example Usage
+
+*Basic example*
+
+```terraform
+resource "azuread_invitation" "example" {
+  user_email_address = "[email protected]"
+  redirect_url       = "https://portal.azure.com"
+}
+```
+
+*Invitation with custom email*
+
+```terraform
+resource "azuread_invitation" "example" {
+  user_display_name  = "Bob Bobson"
+  user_email_address = "[email protected]"
+  redirect_url       = "https://portal.azure.com"
+
+  send_invitation_message = true
+
+  user_message_info {
+    cc_recipients           = ["[email protected]"]
+    customized_message_body = "Hello there! You are invited to join my Azure tenant !"
+    message_language        = "en-US"
+  }
+}
+```
+
+## Argument Reference
+
+The following arguments are supported:
+
+* `redirect_url` - (Required) URL the user should be redirected to once the invitation is redeemed.
+* `send_invitation_message` - (Optional) If `true`, an email wille be sent to the user being invited. Must be set to `true` if a `user_message_info` block is specified. Defaults to `false`.
+* `user_display_name` - (Optional) Display name of the user being invited.
+* `user_email_address` - (Required) Email address of the user being invited.
+* `user_message_info` - (Optional) A `user_message_info` block as documented below, which configures the message being sent to the invited user. `send_invitation_message` must be set to `true` if this block is specified.
+
+---
+
+`user_message_info` block supports the following:
+
+* `cc_recipients` - (Optional) Additional recipients the invitation message should be sent to. Currently only 1 additional recipient is supported by Azure.
+* `customized_message_body` - (Optional) Customized message body you want to send if you don't want the default message.
+* `message_language` - (Optional) Language the message will be sent in. The value specified must be in ISO 639 format. Defaults to `en-US`.
+
+
+## Attributes Reference
+
+In addition to all arguments above, the following attributes are exported:
+
+* `id` - ID of the invitation.
+* `redeem_url` - URL the user can use to redeem the invitation.
+* `user_id` - Object ID of the invited user.