docs: Inter-link documentation mentioning guests.

Make it easier to understand what guests are allowed to do, and how to
make them, by cross-linking the documentation which mentions them.

templates/zerver/help/invite-new-users.md

@@ -1,6 +1,7 @@
 # Invite new users
 
-There are a number of ways to grant access to your Zulip organization.
+There are a number of ways to grant access to your Zulip organization;
+the article below describes each in more detail.
 
 * Allow **anyone to join** without an invitation.
 
@@ -10,7 +11,9 @@ There are a number of ways to grant access to your Zulip organization.
 
 * Share a **reusable invitation link**.
 
-This article will cover these methods in detail.
+The last two, invite-based, techniques also allow you to control the
+[role (admin, member, or guest)](/help/roles-and-permissions) that the
+invited people will have.
 
 You can also manage access by
 [controlling how users authenticate](/help/configure-authentication-methods)
@@ -75,7 +78,8 @@ and reusable invitation links expire 10 days after they are sent.
 
 1. Enter a list of email addresses.
 
-1. Decide whether the users should join as admins, members, or guests.
+1. Decide whether the users should join as [admins, members, or
+   guests](/help/roles-and-permissions).
 
 1. Select which streams they should join. If you send invitations often, you
    may want to configure a set of
@@ -93,8 +97,8 @@ and reusable invitation links expire 10 days after they are sent.
 
 1. Click **Generate invite link**.
 
-1. Decide whether users using the link should join as admins, members, or
-   guests.
+1. Decide whether users using the link should join as [admins,
+   members, or guests](/help/roles-and-permissions).
 
 1. Select which streams they should join. If you send invitations often, you
    may want to configure a set of
@@ -140,3 +144,8 @@ invitation link.
    and invitation links, or **Resend** email invitations.
 
 {end_tabs}
+
+## Related articles
+
+* [Stream permissions](/help/stream-permissions)
+* [Roles and permissions](/help/roles-and-permissions)

templates/zerver/help/roles-and-permissions.md

@@ -11,6 +11,11 @@ There are several roles in a Zulip organization.
 * **Guest**: Can only access streams they've been added to. Cannot create
   new streams.
 
+For details of the access control model, see [Stream
+permissions](/help/stream-permissions).  You can decide what role to
+invite a user as when you [send them an
+invitation](/help/invite-new-users#send-invitations).
+
 ## Billing and guests
 
 Guests are only available on Zulip on-premise and on paid plans for Zulip
@@ -36,3 +41,4 @@ Cloud. There are two kinds of guest for billing purposes:
 ## Related articles
 
 * [Stream permissions](/help/stream-permissions)
+* [Inviting new users](/help/invite-new-users)

templates/zerver/help/stream-permissions.md

@@ -90,3 +90,8 @@ only post to public streams if they are subscribed.
 
 ✶ [Configurable](/help/stream-sending-policy), but at minimum
 must be subscribed to the stream.
+
+## Related articles
+
+* [Roles and permissions](/help/roles-and-permissions)
+* [Stream sending policy](/help/stream-sending-policy)