help: Document upgrade flow, billing, and sponsorship requests.

Documents how to upgrade to a paid plan, manage billing, and
apply for sponsorship.

Fixes #27946.

help/zulip-cloud-billing.md

@@ -1,8 +1,66 @@
 # Zulip Cloud billing
 
 This page answers some frequently asked questions about [Zulip Cloud plans and
-pricing](https://zulip.com/plans/). If you have any other questions, please don't hesitate to
-reach out at sales@zulip.com.
+pricing](https://zulip.com/plans/). If you have any other questions, please
+don't hesitate to reach out at [sales@zulip.com](mailto:sales@zulip.com).
+
+## Upgrade to a Zulip Cloud Standard or Plus plan
+
+{start_tabs}
+
+{tab|zulip-cloud-standard}
+
+{relative|gear|plans}
+
+1. Under the **Cloud Standard** pricing plan, click **Upgrade to Standard**.
+
+1. Select your preferred option from the **Payment schedule** dropdown.
+
+1. Click **Add card** to enter your payment details.
+
+1. Click **Purchase Zulip Cloud Standard**.
+
+{tab|zulip-cloud-plus}
+
+{relative|gear|plans}
+
+1. Under the **Cloud Plus** pricing plan, click **Contact sales**.
+
+{end_tabs}
+
+## Manage billing
+
+{start_tabs}
+
+{tab|desktop-web}
+
+{relative|gear|billing}
+
+{end_tabs}
+
+## Apply for sponsorship
+
+{start_tabs}
+
+{tab|request-sponsorship}
+
+1. Click on the **gear** (<i class="zulip-icon zulip-icon-gear"></i>) icon in
+   the upper right corner of the web or desktop app.
+
+1. Click the **Request sponsorship** link at the top of the gear menu.
+
+1. Fill out the requested information, and click **Submit**.
+
+{tab|request-education-pricing}
+
+1. Click on the **gear** (<i class="zulip-icon zulip-icon-gear"></i>) icon in
+   the upper right corner of the web or desktop app.
+
+1. Click the **Request education pricing** link at the top of the gear menu.
+
+1. Fill out the requested information, and click **Submit**.
+
+{end_tabs}
 
 ## Differences between Zulip Cloud plans
 

zerver/lib/markdown/help_relative_links.py

@@ -28,13 +28,13 @@ gear_info = {
     "integrations": ['<i class="fa fa-github"></i> Integrations', "/integrations/"],
     "stats": ['<i class="fa fa-bar-chart"></i> Usage statistics', "/stats"],
     "plans": ['<i class="fa fa-rocket"></i> Plans and pricing', "/plans/"],
-    "billing": ['<i class="fa fa-credit-card"></i> Billing', "/billing/"],
+    "billing": ['<i class="zulip-icon zulip-icon-credit-card"></i> Billing', "/billing/"],
     "about-zulip": ["About Zulip", "/#about-zulip"],
 }
 
 gear_instructions = """
-1. Click on the **gear** (<i class="fa fa-cog"></i>) icon in the upper
-   right corner of the web or desktop app.
+1. Click on the **gear** (<i class="zulip-icon zulip-icon-gear"></i>) icon in
+   the upper right corner of the web or desktop app.
 
 1. Select {item}.
 """

zerver/lib/markdown/tabbed_sections.py

@@ -86,6 +86,10 @@ TAB_SECTION_LABELS = {
     "via-stream-settings": "Via stream settings",
     "default-subdomain": "Default subdomain",
     "custom-subdomain": "Custom subdomain",
+    "zulip-cloud-standard": "Zulip Cloud Standard",
+    "zulip-cloud-plus": "Zulip Cloud Plus",
+    "request-sponsorship": "Request sponsorship",
+    "request-education-pricing": "Request education pricing",
     "zulip-cloud": "Zulip Cloud",
     "self-hosting": "Self hosting",
     "okta": "Okta",