more social card tweaks, and include in RSS as well (#2599)

* move link expander to new file, add test, refactor a bit

* text formatting: include indication if a quote post exists

* rss: include expanded links

bskyweb/cmd/bskyweb/formatting_test.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+	"encoding/json"
+	"io"
+	"os"
+	"strings"
+	"testing"
+
+	appbsky "github.com/bluesky-social/indigo/api/bsky"
+)
+
+func loadPost(t *testing.T, p string) appbsky.FeedPost {
+
+	f, err := os.Open(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() { _ = f.Close() }()
+
+	postBytes, err := io.ReadAll(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var post appbsky.FeedPost
+	if err := json.Unmarshal(postBytes, &post); err != nil {
+		t.Fatal(err)
+	}
+	return post
+}
+
+func TestExpandPostText(t *testing.T) {
+	post := loadPost(t, "testdata/atproto_embed_post.json")
+
+	text := ExpandPostText(&post)
+	if !strings.Contains(text, "https://github.com/snarfed/bridgy-fed") {
+		t.Fail()
+	}
+}