move nostr-sdk repository into here because why not?

sdk/follows.go

@@ -0,0 +1,50 @@
+package sdk
+
+import (
+	"context"
+	"net/url"
+	"strings"
+
+	"github.com/nbd-wtf/go-nostr"
+)
+
+type FollowList = GenericList[Follow]
+
+type Follow struct {
+	Pubkey  string
+	Relay   string
+	Petname string
+}
+
+func (f Follow) Value() string { return f.Pubkey }
+
+func (sys *System) FetchFollowList(ctx context.Context, pubkey string) FollowList {
+	fl, _ := fetchGenericList[Follow](sys, ctx, pubkey, 3, parseFollow, sys.FollowListCache, false)
+	return fl
+}
+
+func parseFollow(tag nostr.Tag) (fw Follow, ok bool) {
+	if len(tag) < 2 {
+		return fw, false
+	}
+	if tag[0] != "p" {
+		return fw, false
+	}
+
+	fw.Pubkey = tag[1]
+	if !nostr.IsValidPublicKey(fw.Pubkey) {
+		return fw, false
+	}
+
+	if len(tag) > 2 {
+		if _, err := url.Parse(tag[2]); err == nil {
+			fw.Relay = nostr.NormalizeURL(tag[2])
+		}
+		if len(tag) > 3 {
+			fw.Petname = strings.TrimSpace(tag[3])
+		}
+		return fw, true
+	}
+
+	return fw, false
+}