api/masto/instance: add short_description field

Added in Mastodon 2.9.2 (June 2019) this is plain-text-only and supposed
to be shorter compared to the older description field.
Some clients were reported to require this field to properly function.

Reported-by: https://akkoma.dev/paulyd

config/config.exs

@@ -194,7 +194,10 @@
   name: "Akkoma",
   email: "example@example.com",
   notify_email: "noreply@example.com",
+  # allowed to use HTML (if short_description is set)
   description: "Akkoma: The cooler fediverse server",
+  # only plain text (defaults to description)
+  short_description: nil,
   background_image: "/images/city.jpg",
   instance_thumbnail: "/instance/thumbnail.jpeg",
   limit: 5_000,

config/description.exs

@@ -566,7 +566,16 @@
         key: :description,
         type: :string,
         description:
-          "The instance's description. It can be seen in nodeinfo and `/api/v1/instance`",
+          "The instance's description. It may use HTML and can be seen in `/api/v1/instance` and nodeifno if no short description is set",
+        suggestions: [
+          "Very cool instance"
+        ]
+      },
+      %{
+        key: :short_description,
+        type: :string,
+        description:
+          "A brief instance description. It must be plain text and can be seen in `/api/v1/instance` and nodeinfo",
         suggestions: [
           "Very cool instance"
         ]

docs/docs/configuration/cheatsheet.md

@@ -12,7 +12,12 @@ To add configuration to your config file, you can copy it from the base config.
 * `name`: The instance’s name.
 * `email`: Email used to reach an Administrator/Moderator of the instance.
 * `notify_email`: Email used for notifications.
-* `description`: The instance’s description, can be seen in nodeinfo and `/api/v1/instance`.
+* `short_description`: A brief, plain-text-only instance description.
+    Can be seen in nodeinfo and `/api/v1/instance`.
+    Defaults to `description` if unset
+* `description`: The instance’s more detailed description.
+    This is allowed to use HTML if `short_description` is set.
+    Can be seen in `api/v1/instance`.
 * `limit`: Posts character limit (CW/Subject included in the counter).
 * `description_limit`: The character limit for image descriptions.
 * `remote_limit`: Hard character limit beyond which remote posts will be dropped.

lib/pleroma/web/mastodon_api/views/instance_view.ex

@@ -17,6 +17,8 @@ def render("show.json", _) do
       uri: Pleroma.Web.Endpoint.url(),
       title: Keyword.get(instance, :name),
       description: Keyword.get(instance, :description),
+      short_description:
+        Keyword.get(instance, :short_description) || Keyword.get(instance, :description),
       version: "#{@mastodon_api_level} (compatible; #{Pleroma.Application.named_version()})",
       email: Keyword.get(instance, :email),
       urls: %{

lib/pleroma/web/nodeinfo/nodeinfo.ex

@@ -9,6 +9,12 @@ defmodule Pleroma.Web.Nodeinfo.Nodeinfo do
   alias Pleroma.Web.Federator.Publisher
   alias Pleroma.Web.MastodonAPI.InstanceView
 
+  defp description() do
+    # The text in nodeinfo should be plain text and preferably not too long
+    Config.get([:instance, :short_description]) ||
+      Config.get([:instance, :description])
+  end
+
   # returns a nodeinfo 2.0 map, since 2.1 just adds a repository field
   # under software.
   def get_nodeinfo("2.0") do
@@ -43,7 +49,7 @@ def get_nodeinfo("2.0") do
       },
       metadata: %{
         nodeName: Config.get([:instance, :name]),
-        nodeDescription: Config.get([:instance, :description]),
+        nodeDescription: description(),
         private: !Config.get([:instance, :public], true),
         suggestions: %{
           enabled: false

test/pleroma/web/mastodon_api/controllers/instance_controller_test.exs

@@ -23,6 +23,7 @@ test "get instance information", %{conn: conn} do
              "uri" => _,
              "title" => _,
              "description" => _,
+             "short_description" => _,
              "version" => _,
              "email" => from_config_email,
              "urls" => %{