fix(slack): add channels:join scope and fix zero-value last_sync bug

handlers/integrations.go

@@ -138,7 +138,7 @@ func SlackAuth(w http.ResponseWriter, r *http.Request) {
 	redirectURI := getSlackRedirectURI(r)
 	authURL := "https://slack.com/oauth/v2/authorize?" +
 		"client_id=" + slackClientID +
-		"&scope=channels:history,channels:read,chat:write,users:read,groups:read,im:history,groups:history" +
+		"&scope=channels:history,channels:read,chat:write,users:read,groups:read,im:history,groups:history,channels:join" +
 		"&redirect_uri=" + redirectURI +
 		"&state=" + state
 

services/slack.go

@@ -20,9 +20,14 @@ const (
 	SlackAPIBaseURL = "https://slack.com/api"
 )
 
+// HTTPDoer abstracts the HTTP client for testability.
+type HTTPDoer interface {
+	Do(req *http.Request) (*http.Response, error)
+}
+
 // SlackClient handles interactions with the Slack API
 type SlackClient struct {
-	HTTPClient *http.Client
+	HTTPClient HTTPDoer
 	BaseURL    string
 }