created tracker api endpoint and created UI interface for trackers

server/internal/models/user_tracker.go

@@ -0,0 +1,12 @@
+package models
+
+import "time"
+
+type UserTracker struct {
+	UserID      uint   `gorm:"primaryKey;index;not null"`
+	TrackerGUID string `gorm:"primaryKey;size:64;index;not null"`
+	CreatedAt   time.Time
+
+	User    User    `gorm:"constraint:OnDelete:CASCADE;"`
+	Tracker Tracker `gorm:"constraint:OnDelete:CASCADE;foreignKey:TrackerGUID;references:GUID"`
+}