Fediverse-based authentication (#1846)

* Able to authenticate user against IndieAuth. For #1273

* WIP server indieauth endpoint. For https://github.com/owncast/owncast/issues/1272

* Add migration to remove access tokens from user

* Add authenticated bool to user for display purposes

* Add indieauth modal and auth flair to display names. For #1273

* Validate URLs and display errors

* Renames, cleanups

* Handle relative auth endpoint paths. Add error handling for missing redirects.

* Disallow using display names in use by registered users. Closes #1810

* Verify code verifier via code challenge on callback

* Use relative path to authorization_endpoint

* Post-rebase fixes

* Use a timestamp instead of a bool for authenticated

* Propertly handle and display error in modal

* Use auth'ed timestamp to derive authenticated flag to display in chat

* Fediverse chat auth via OTP

* Increase validity time just in case

* Add fediverse auth into auth modal

* Text, validation, cleanup updates for fedi auth

* Fix typo

* Remove unused images

* Remove unused file

* Add chat display name to auth modal text

activitypub/webfinger/webfinger.go

@@ -0,0 +1,46 @@
+package webfinger
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/url"
+	"strings"
+)
+
+// GetWebfingerLinks will return webfinger data for an account.
+func GetWebfingerLinks(account string) ([]map[string]interface{}, error) {
+	type webfingerResponse struct {
+		Links []map[string]interface{} `json:"links"`
+	}
+
+	account = strings.TrimLeft(account, "@") // remove any leading @
+	accountComponents := strings.Split(account, "@")
+	fediverseServer := accountComponents[1]
+
+	// HTTPS is required.
+	requestURL, err := url.Parse("https://" + fediverseServer)
+	if err != nil {
+		return nil, fmt.Errorf("unable to parse fediverse server host %s", fediverseServer)
+	}
+
+	requestURL.Path = "/.well-known/webfinger"
+	query := requestURL.Query()
+	query.Add("resource", fmt.Sprintf("acct:%s", account))
+	requestURL.RawQuery = query.Encode()
+
+	response, err := http.DefaultClient.Get(requestURL.String())
+	if err != nil {
+		return nil, err
+	}
+
+	defer response.Body.Close()
+
+	var links webfingerResponse
+	decoder := json.NewDecoder(response.Body)
+	if err := decoder.Decode(&links); err != nil {
+		return nil, err
+	}
+
+	return links.Links, nil
+}