feat: self-service user signup (#672)

Co-authored-by: Elias Schneider <login@eliasschneider.com>

backend/internal/model/app_config.go

@@ -38,6 +38,7 @@ type AppConfig struct {
 	AccentColor         AppConfigVariable `key:"accentColor,public"`         // Public
 	DisableAnimations   AppConfigVariable `key:"disableAnimations,public"`   // Public
 	AllowOwnAccountEdit AppConfigVariable `key:"allowOwnAccountEdit,public"` // Public
+	AllowUserSignups    AppConfigVariable `key:"allowUserSignups,public"`    // Public
 	// Internal
 	BackgroundImageType AppConfigVariable `key:"backgroundImageType,internal"` // Internal
 	LogoLightImageType  AppConfigVariable `key:"logoLightImageType,internal"`  // Internal

backend/internal/model/audit_log.go

@@ -28,6 +28,7 @@ type AuditLogEvent string //nolint:recvcheck
 const (
 	AuditLogEventSignIn                     AuditLogEvent = "SIGN_IN"
 	AuditLogEventOneTimeAccessTokenSignIn   AuditLogEvent = "TOKEN_SIGN_IN"
+	AuditLogEventAccountCreated             AuditLogEvent = "ACCOUNT_CREATED"
 	AuditLogEventClientAuthorization        AuditLogEvent = "CLIENT_AUTHORIZATION"
 	AuditLogEventNewClientAuthorization     AuditLogEvent = "NEW_CLIENT_AUTHORIZATION"
 	AuditLogEventDeviceCodeAuthorization    AuditLogEvent = "DEVICE_CODE_AUTHORIZATION"

backend/internal/model/signup_token.go

@@ -0,0 +1,28 @@
+package model
+
+import (
+	"time"
+
+	datatype "github.com/pocket-id/pocket-id/backend/internal/model/types"
+)
+
+type SignupToken struct {
+	Base
+
+	Token      string            `json:"token"`
+	ExpiresAt  datatype.DateTime `json:"expiresAt" sortable:"true"`
+	UsageLimit int               `json:"usageLimit" sortable:"true"`
+	UsageCount int               `json:"usageCount" sortable:"true"`
+}
+
+func (st *SignupToken) IsExpired() bool {
+	return time.Time(st.ExpiresAt).Before(time.Now())
+}
+
+func (st *SignupToken) IsUsageLimitReached() bool {
+	return st.UsageCount >= st.UsageLimit
+}
+
+func (st *SignupToken) IsValid() bool {
+	return !st.IsExpired() && !st.IsUsageLimitReached()
+}