integrations-doc: Update URL specification section for incoming webhooks.

Revises section to use headers for the possible parameters so that
they can be linked to directly from other documentation pages.

Updates base URL text to read more clearly when rendered.

api_docs/incoming-webhooks-overview.md

@@ -156,51 +156,61 @@ below are for a webhook named `MyWebHook`.
   spot why something isn't working or if the service is using custom HTTP
   headers.
 
-## URLs
+## URL specification
 
-The base URL for an incoming webhook integration bot is
-`{{ api_url }}/v1/external/INTEGRATION_NAME?api_key=API_KEY` where
+The base URL for an incoming webhook integration bot, where
 `INTEGRATION_NAME` is the name of the specific webhook integration and
 `API_KEY` is the API key of the bot created by the user for the
-integration.
+integration, is:
 
-The list of existing webhook integrations can be found in
-`zerver/lib/integrations.py` (at `WEBHOOK_INTEGRATIONS`) or by browsing
-the [Integrations documentation](/integrations/).
+```
+{{ api_url }}/v1/external/INTEGRATION_NAME?api_key=API_KEY
+```
+
+The list of existing webhook integrations can be found by browsing the
+[Integrations documentation](/integrations/) or in
+`zerver/lib/integrations.py` at `WEBHOOK_INTEGRATIONS`.
 
 Parameters accepted in the URL include:
 
-* `api_key`: **Required**. The API key of the bot created by the user
-  for the integration. To get a bot's API key, see the [API
-  keys](/api/api-keys) documentation.
+### api_key *(required)*
 
-* `stream`: The stream for the integration to send notifications to.
-  Can be either the stream ID or the [URL-encoded][url-encoder] stream
-  name. By default the integration will send direct messages to the
-  bot's owner.
+The API key of the bot created by the user for the integration. To get a
+bot's API key, see the [API keys](/api/api-keys) documentation.
 
-    !!! tip ""
+### stream
 
-        A stream ID can be found when [browsing streams][browse-streams]
-        in the web app via the URL.
+The stream for the integration to send notifications to. Can be either
+the stream ID or the [URL-encoded][url-encoder] stream name. By default
+the integration will send direct messages to the bot's owner.
 
-* `topic`: The topic in the specified stream for the integration to
-  send notifications to. The topic should also be
-  [URL-encoded][url-encoder]. By default the integration will have a
-  topic configured for stream messages.
+!!! tip ""
 
-* `only_events`, `exclude_events`: Some incoming webhook integrations support
-  these parameters to filter which events will trigger a notification. You can
-  append either `&only_events=["event_a","event_b"]` or
-  `&exclude_events=["event_a","event_b"]` (or both, with different events) to
-  the URL, with an arbitrary number of supported events. You can use UNIX-style
-  wildcards like `*` to include multiple events. For example, `test*` matches
-  every event that starts with `test`.
+    A stream ID can be found when [browsing streams][browse-streams]
+    in the web app via the URL.
 
-    !!! tip ""
+### topic
 
-        For a list of supported events, see the integration's [integration
-        documentation](/integrations) page.
+The topic in the specified stream for the integration to send
+notifications to. The topic should also be [URL-encoded][url-encoder].
+By default the integration will have a topic configured for stream
+messages.
+
+### only_events, exclude_events
+
+Some incoming webhook integrations support these parameters to filter
+which events will trigger a notification. You can append either
+`&only_events=["event_a","event_b"]` or
+`&exclude_events=["event_a","event_b"]` (or both, with different events)
+to the URL, with an arbitrary number of supported events.
+
+You can use UNIX-style wildcards like `*` to include multiple events.
+For example, `test*` matches every event that starts with `test`.
+
+!!! tip ""
+
+    For a list of supported events, see a specific [integration's
+    documentation](/integrations) page.
 
 [browse-streams]: /help/browse-and-subscribe-to-streams
 [add-bot]: /help/add-a-bot-or-integration

templates/zerver/integrations/include/event-filtering-additional-feature.md

@@ -1,8 +1,10 @@
 ### Filtering incoming events
 
-The {{ integration_display_name }} integration supports filtering for
-the following events:
+The {{ integration_display_name }} integration supports
+[filtering][event-filters] for the following events:
 
 {% set comma = joiner(", ") %}
 
 {% for event_type in all_event_types -%} {{- comma() -}} `{{ event_type }}` {%- endfor %}
+
+[event-filters]: /api/incoming-webhooks-overview#only_events-exclude_events

templates/zerver/integrations/include/generate-integration-url.md

@@ -15,4 +15,4 @@ The generated URL will look something like this:
 see [the webhook URLs specification][incoming-webhook-urls].*
 
 [generate-url]: /help/generate-integration-url
-[incoming-webhook-urls]: /api/incoming-webhooks-overview#urls
+[incoming-webhook-urls]: /api/incoming-webhooks-overview#url-specification

templates/zerver/integrations/include/webhooks-url-specification.md

@@ -1,3 +1,3 @@
 * [Webhook URLs specification][incoming-webhook-urls]
 
-[incoming-webhook-urls]: /api/incoming-webhooks-overview#urls
+[incoming-webhook-urls]: /api/incoming-webhooks-overview#url-specification