Add API endpoint /api/pleroma/follow_export to get your followers in Mastodon-compatible CSV format

This is the same format we support for importing users.

lib/pleroma/web/pleroma_api/controllers/user_export_controller.ex

@@ -0,0 +1,28 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2022 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.PleromaAPI.UserExportController do
+  use Pleroma.Web, :controller
+
+  require Logger
+
+  alias Pleroma.User
+  alias Pleroma.Web.Plugs.OAuthScopesPlug
+
+  plug(OAuthScopesPlug, %{scopes: ["follow", "read:follows"]} when action == :following)
+
+  @following_accounts_header "Account address,Show boosts,Notify on new posts,Languages\n"
+
+  def following(%{assigns: %{user: follower}} = conn, _) do
+    friends = User.get_friends_nicknames(follower) |> Enum.join(",true,false,\n")
+
+    csv_data = @following_accounts_header <> friends <> ",true,false,"
+
+    conn
+    |> put_resp_content_type("text/csv")
+    |> put_resp_header("content-disposition", "attachment; filename=\"following_accounts.csv\"")
+    |> put_root_layout(false)
+    |> send_resp(200, csv_data)
+  end
+end

lib/pleroma/web/router.ex

@@ -364,6 +364,8 @@ defmodule Pleroma.Web.Router do
     post("/blocks_import", UserImportController, :blocks)
     post("/follow_import", UserImportController, :follow)
 
+    get("/follow_export", UserExportController, :following)
+
     get("/accounts/mfa", TwoFactorAuthenticationController, :settings)
     get("/accounts/mfa/backup_codes", TwoFactorAuthenticationController, :backup_codes)
     get("/accounts/mfa/setup/:method", TwoFactorAuthenticationController, :setup)