feat: add sqlite database for storing sessions (#326)

* feat: add sqlite database for storing sessions

* refactor: use db instance instead of service in auth service

* fix: coderabbit suggestions

internal/model/session_model.go

@@ -0,0 +1,12 @@
+package model
+
+type Session struct {
+	UUID        string `gorm:"column:uuid;primaryKey"`
+	Username    string `gorm:"column:username"`
+	Email       string `gorm:"column:email"`
+	Name        string `gorm:"column:name"`
+	Provider    string `gorm:"column:provider"`
+	TOTPPending bool   `gorm:"column:totp_pending"`
+	OAuthGroups string `gorm:"column:oauth_groups"`
+	Expiry      int64  `gorm:"column:expiry"`
+}