fix: move implementation to "internal" package

internal/types/transaction.go

@@ -0,0 +1,41 @@
+package types
+
+import (
+	"time"
+
+	"github.com/google/uuid"
+)
+
+// At the center of the application is the transaction.
+//
+// Every piece of data should be calculated based on transactions.
+// This means potential calculation errors can be fixed later in time.
+//
+// If it becomes necessary to precalculate snapshots for performance reasons, this can be done in the future.
+// But the transaction should always be the source of truth.
+type Transaction struct {
+	Id     uuid.UUID `db:"id"`
+	UserId uuid.UUID `db:"user_id"`
+
+	Timestamp   time.Time `db:"timestamp"`
+	Party       string    `db:"party"`
+	Description string    `db:"description"`
+
+	AccountId       *uuid.UUID `db:"account_id"`
+	TreasureChestId *uuid.UUID `db:"treasure_chest_id"`
+	Value           int64      `db:"value"`
+
+	// If an error is present, then the transaction is not valid and should not be used for calculations.
+	Error     *string   `db:"error"`
+	CreatedAt time.Time `db:"created_at"`
+	// Either a user_id or a transaction_recurring_id
+	CreatedBy uuid.UUID  `db:"created_by"`
+	UpdatedAt *time.Time `db:"updated_at"`
+	UpdatedBy *uuid.UUID `db:"updated_by"`
+}
+
+type TransactionItemsFilter struct {
+	AccountId       string
+	TreasureChestId string
+	Error           string
+}