MastoAPI AccountView: fill source.note with plaintext version of note

Closes: https://git.pleroma.social/pleroma/pleroma/issues/926

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

@@ -112,7 +112,7 @@ defp do_render("account.json", %{user: user} = opts) do
       fields: fields,
       bot: bot,
       source: %{
-        note: "",
+        note: HTML.strip_tags((user.bio || "") |> String.replace("<br>", "\n")),
         sensitive: false,
         pleroma: %{}
       },

test/web/mastodon_api/account_view_test.exs

@@ -55,7 +55,7 @@ test "Represent a user account" do
       fields: [],
       bot: false,
       source: %{
-        note: "",
+        note: "valid html",
         sensitive: false,
         pleroma: %{}
       },
@@ -120,7 +120,7 @@ test "Represent a Service(bot) account" do
       fields: [],
       bot: true,
       source: %{
-        note: "",
+        note: user.bio,
         sensitive: false,
         pleroma: %{}
       },
@@ -209,7 +209,7 @@ test "represent an embedded relationship" do
       fields: [],
       bot: true,
       source: %{
-        note: "",
+        note: user.bio,
         sensitive: false,
         pleroma: %{}
       },