satellite/payments: slightly refactor user upgrade observer of billing chore

Resolves post-merge comments from here
https://review.dev.storj.io/c/storj/storj/+/10780

Reworked some definitions. Added checks and comments.

Change-Id: I19c63804ad1f30a1ffd8cb87e96f43deed20a685

satellite/core.go

@@ -519,8 +519,8 @@ func New(log *zap.Logger, full *identity.FullIdentity, db DB,
 			debug.Cycle("Payments Storjscan", peer.Payments.StorjscanChore.TransactionCycle),
 		)
 
-		choreObservers := map[billing.ObserverBilling]billing.Observer{
-			billing.ObserverUpgradeUser: console.NewUpgradeUserObserver(peer.DB.Console(), peer.DB.Billing(), config.Console.UsageLimits, config.Console.UserBalanceForUpgrade),
+		choreObservers := billing.ChoreObservers{
+			UpgradeUser: console.NewUpgradeUserObserver(peer.DB.Console(), peer.DB.Billing(), config.Console.UsageLimits, config.Console.UserBalanceForUpgrade),
 		}
 
 		peer.Payments.BillingChore = billing.NewChore(

satellite/payments/billing/chore.go

@@ -13,13 +13,16 @@ import (
 	"storj.io/common/sync2"
 )
 
-// ObserverBilling used to create enumerable of chore observers.
-type ObserverBilling int64
+// Observer processes a billing transaction.
+type Observer interface {
+	// Process is called repeatedly for each transaction.
+	Process(context.Context, Transaction) error
+}
 
-const (
-	// ObserverUpgradeUser stands for upgrade user observer type.
-	ObserverUpgradeUser ObserverBilling = 0
-)
+// ChoreObservers holds functionality to process confirmed transactions using different types of observers.
+type ChoreObservers struct {
+	UpgradeUser Observer
+}
 
 // ChoreErr is billing chore err class.
 var ChoreErr = errs.Class("billing chore")
@@ -35,11 +38,11 @@ type Chore struct {
 
 	disableLoop bool
 	bonusRate   int64
-	observers   map[ObserverBilling]Observer
+	observers   ChoreObservers
 }
 
 // NewChore creates new chore.
-func NewChore(log *zap.Logger, paymentTypes []PaymentType, transactionsDB TransactionsDB, interval time.Duration, disableLoop bool, bonusRate int64, observers map[ObserverBilling]Observer) *Chore {
+func NewChore(log *zap.Logger, paymentTypes []PaymentType, transactionsDB TransactionsDB, interval time.Duration, disableLoop bool, bonusRate int64, observers ChoreObservers) *Chore {
 	return &Chore{
 		log:              log,
 		paymentTypes:     paymentTypes,
@@ -84,8 +87,15 @@ func (chore *Chore) Run(ctx context.Context) (err error) {
 					break
 				}
 
-				err = chore.observers[ObserverUpgradeUser].Process(ctx, transaction)
+				if chore.observers.UpgradeUser == nil {
+					continue
+				}
+
+				err = chore.observers.UpgradeUser.Process(ctx, transaction)
 				if err != nil {
+					// we don't want to halt storing transactions if upgrade user observer fails
+					// because this chore is designed to store new transactions.
+					// So auto upgrading user is a side effect which shouldn't interrupt the main process.
 					chore.log.Error("error upgrading user", zap.Error(ChoreErr.Wrap(err)))
 				}
 			}

satellite/payments/billing/chore_test.go

@@ -85,8 +85,8 @@ func TestChore(t *testing.T) {
 			),
 		}
 
-		choreObservers := map[billing.ObserverBilling]billing.Observer{
-			billing.ObserverUpgradeUser: console.NewUpgradeUserObserver(consoleDB, db, usageLimitsConfig, userBalanceForUpgrade),
+		choreObservers := billing.ChoreObservers{
+			UpgradeUser: console.NewUpgradeUserObserver(consoleDB, db, usageLimitsConfig, userBalanceForUpgrade),
 		}
 
 		chore := billing.NewChore(zaptest.NewLogger(t), paymentTypes, db, time.Hour, false, bonusRate, choreObservers)
@@ -168,8 +168,8 @@ func TestChore_UpgradeUserObserver(t *testing.T) {
 		_, err = sat.AddProject(ctx, user.ID, "Test Project")
 		require.NoError(t, err)
 
-		choreObservers := map[billing.ObserverBilling]billing.Observer{
-			billing.ObserverUpgradeUser: console.NewUpgradeUserObserver(db.Console(), db.Billing(), sat.Config.Console.UsageLimits, sat.Config.Console.UserBalanceForUpgrade),
+		choreObservers := billing.ChoreObservers{
+			UpgradeUser: console.NewUpgradeUserObserver(db.Console(), db.Billing(), sat.Config.Console.UsageLimits, sat.Config.Console.UserBalanceForUpgrade),
 		}
 
 		amount1 := int64(200) // $2

satellite/payments/billing/observer.go

@@ -1,12 +0,0 @@
-// Copyright (C) 2023 Storj Labs, Inc.
-// See LICENSE for copying information.
-
-package billing
-
-import "context"
-
-// Observer processes a billing transaction.
-type Observer interface {
-	// Process is called repeatedly for each transaction.
-	Process(context.Context, Transaction) error
-}