markdown: Add indented versions of multi-line Markdown macros.

This is part of our efforts to change our integrations/webhooks
docs to follow the same sort of numbered-list format as our /help
docs. In order to indicate that paragraphs separated by newlines
are part of the same numbered-list point, every paragraph must be
indented 4 spaces.

templates/zerver/help/include/change-zulip-config-file-indented.md

@@ -0,0 +1,13 @@
+    On your {{ settings_html|safe }}, create a bot for
+    {{ integration_display_name }}.
+
+    Next, open
+    `integrations/{{ integration_name }}/zulip_{{ integration_name }}_config.py`
+    with your favorite editor, and change the following lines to specify the
+    email address and API key for your {{ integration_display_name }} bot:
+
+    ```
+    ZULIP_USER = "{{ integration_name }}-bot@example.com"
+    ZULIP_API_KEY = "0123456789abcdef0123456789abcdef"
+    ZULIP_SITE = "{{ api_url }}"
+    ```

templates/zerver/help/include/create-bot-construct-url-indented.md

@@ -0,0 +1,20 @@
+    Next, on your {{ settings_html|safe }},
+    [create a bot](/help/add-a-bot-or-integration) for
+    {{ integration_display_name }}. Make sure that you select
+    **Incoming webhook** as the **Bot type**:
+
+    ![](/static/images/help/bot_types.png)
+
+    The API keys for "Incoming webhook" bots are limited to only
+    sending messages via webhooks. Thus, this bot type lessens
+    the security risks associated with exposing the bot's API
+    key to third-party services.
+
+    Construct the URL for the {{ integration_display_name }}
+    bot using the bot API key and stream name:
+
+    {!webhook-url.md!}
+
+    Modify the parameters of the URL above, where `api_key` is the API key
+    of your Zulip bot, and `stream` is the stream name you want the
+    notifications sent to.

templates/zerver/help/include/git-webhook-url-with-branches-indented.md

@@ -0,0 +1,4 @@
+    You can also limit the branches you receive notifications for by
+    specifying them in a comma-separated list at the end of the URL,
+    like so:
+    `{{ api_url }}{{ integration_url }}?api_key=abcdefgh&stream={{ recommended_stream_name }}&branches=master,development`

templates/zerver/help/include/webhook-url-with-bot-email-indented.md

@@ -0,0 +1,7 @@
+    In the URL field, enter:
+
+    `{{ external_uri_scheme }}bot_email:bot_api_key@{{ api_url_scheme_relative }}{{ integration_url }}`
+
+    Replace `bot_email` and `bot_api_key` above with the URL-encoded email
+    address and API key of the bot.  To URL-encode the email address, you
+    just need to replace `@` in the bot's email address with `%40`.

tools/linter_lib/custom_check.py

@@ -699,6 +699,8 @@ def build_custom_checkers(by_lang):
             "templates/zerver/integrations/perforce.md",
             # Has some example code that could perhaps be wrapped
             "templates/zerver/api/webhook-walkthrough.md",
+            # This macro has a long indented URL
+            "templates/zerver/help/include/git-webhook-url-with-branches-indented.md",
         }
         for fn in by_lang['md']:
             max_length = None