Add queued email notifications for collaboration events

apps/server/internal/config/config.go

@@ -38,9 +38,31 @@ type AuthConfig struct {
 }
 
 type EmailConfig struct {
-	SMTPHost string `json:"smtpHost"`
-	SMTPPort int    `json:"smtpPort"`
-	From     string `json:"from"`
+	// Provider selects the sender implementation. Valid values: "noop",
+	// "smtp", "postmark". When empty, the loader infers from the other
+	// fields: PostmarkToken wins, then SMTPHost, then NoOp.
+	Provider       string `json:"provider"`
+	SMTPHost       string `json:"smtpHost"`
+	SMTPPort       int    `json:"smtpPort"`
+	PostmarkToken  string `json:"postmarkToken"`
+	PostmarkAPIURL string `json:"postmarkApiUrl"`
+	From           string `json:"from"`
+	InstanceName   string `json:"instanceName"`
+}
+
+// ResolvedProvider returns the concrete provider choice after applying the
+// inference rule. Operators can set Provider explicitly to force a choice.
+func (e EmailConfig) ResolvedProvider() string {
+	if e.Provider != "" {
+		return e.Provider
+	}
+	if e.PostmarkToken != "" {
+		return "postmark"
+	}
+	if e.SMTPHost != "" {
+		return "smtp"
+	}
+	return "noop"
 }
 
 func Default() Config {
@@ -59,9 +81,10 @@ func Default() Config {
 			PublicOrigin: "http://localhost:8080",
 		},
 		Email: EmailConfig{
-			SMTPHost: "localhost",
-			SMTPPort: 1025,
-			From:     "notifications@cairnquire.local",
+			SMTPHost:     "localhost",
+			SMTPPort:     1025,
+			From:         "notifications@cairnquire.local",
+			InstanceName: "Cairnquire",
 		},
 		LogLevel: "INFO",
 	}
@@ -87,6 +110,10 @@ func Load() (Config, error) {
 	overrideString(&cfg.Content.StoreDir, "CAIRNQUIRE_CONTENT_STORE_DIR")
 	overrideString(&cfg.Auth.PublicOrigin, "CAIRNQUIRE_PUBLIC_ORIGIN")
 	overrideString(&cfg.Email.SMTPHost, "CAIRNQUIRE_EMAIL_SMTP_HOST")
+	overrideString(&cfg.Email.PostmarkToken, "CAIRNQUIRE_EMAIL_POSTMARK_TOKEN")
+	overrideString(&cfg.Email.PostmarkAPIURL, "CAIRNQUIRE_EMAIL_POSTMARK_API_URL")
+	overrideString(&cfg.Email.Provider, "CAIRNQUIRE_EMAIL_PROVIDER")
+	overrideString(&cfg.Email.InstanceName, "CAIRNQUIRE_INSTANCE_NAME")
 	if port := os.Getenv("CAIRNQUIRE_EMAIL_SMTP_PORT"); port != "" {
 		if p, err := strconv.Atoi(port); err == nil {
 			cfg.Email.SMTPPort = p