yet more RSS tweaks (#2289)

* rss: full URL in RSS link; use request Host in URLs

Full URL syntax on request from third parties.

Using the actual request host should fix issues with non-bsky-production
deployments. It is HTTPS-only, so doesn't work perfectly for local dev.

* rss: make /profile/{handle}/rss an HTTP redirect

Motivation is easier discoverability of RSS feed.

bskyweb/cmd/bskyweb/server.go

@@ -210,7 +210,7 @@ func serve(cctx *cli.Context) error {
 	e.GET("/profile/:handle/feed/:rkey/liked-by", server.WebGeneric)
 
 	// profile RSS feed (DID not handle)
-	e.GET("/profile/:did/rss", server.WebProfileRSS)
+	e.GET("/profile/:ident/rss", server.WebProfileRSS)
 
 	// post endpoints; only first populates info
 	e.GET("/profile/:handle/post/:rkey", server.WebPost)
@@ -370,6 +370,7 @@ func (srv *Server) WebProfile(c echo.Context) error {
 	req := c.Request()
 	data["profileView"] = pv
 	data["requestURI"] = fmt.Sprintf("https://%s%s", req.Host, req.URL.Path)
+	data["requestHost"] = req.Host
 	return c.Render(http.StatusOK, "profile.html", data)
 }