feat(api): Add alert path prefix as configuration field (#648)

# Description
This PR simply introduces a new configuration field for the Merlin API
server to make the alert path prefix (currently hardcoded as
`alerts/merlin`) into a configurable field. This allows for more
customisable paths to be used when setting up alerts using the current
GitOps approach.

# Modifications
- `api/config/config.go` - Added a new configuration field
`AlertPathPrefix`
- `api/service/model_endpoint_alert_service.go` - Made changes to the
current way an alert file path is generated

# Tests
<!-- Besides the existing / updated automated tests, what specific
scenarios should be tested? Consider the backward compatibility of the
changes, whether corner cases are covered, etc. Please describe the
tests and check the ones that have been completed. Eg:
- [x] Deploying new and existing standard models
- [ ] Deploying PyFunc models
-->

# Checklist
- [x] Added PR label
- [x] Added unit test, integration, and/or e2e tests
- [x] Tested locally
- [ ] Updated documentation
- [ ] Update Swagger spec if the PR introduce API changes
- [ ] Regenerated Golang and Python client if the PR introduces API
changes

# Release Notes
<!--
Does this PR introduce a user-facing change?
If no, just write "NONE" in the release-note block below.
If yes, a release note is required. Enter your extended release note in
the block below.
If the PR requires additional action from users switching to the new
release, include the string "action required".

For more information about release notes, see kubernetes' guide here:
http://git.k8s.io/community/contributors/guide/release-notes.md
-->

```release-note
NONE
```

Author: deadlycoconuts

api/cmd/api/main.go

@@ -320,7 +320,7 @@ func buildDependencies(ctx context.Context, cfg *config.Config, db *gorm.DB, dis
 	modelEndpointAlertService := service.NewModelEndpointAlertService(
 		storage.NewAlertStorage(db), gitlabClient, wardenClient,
 		gitlabConfig.DashboardRepository, gitlabConfig.DashboardBranch,
-		gitlabConfig.AlertRepository, gitlabConfig.AlertBranch,
+		gitlabConfig.AlertRepository, gitlabConfig.AlertBranch, gitlabConfig.AlertPathPrefix,
 		cfg.FeatureToggleConfig.MonitoringConfig.MonitoringBaseURL)
 
 	mlflowConfig := cfg.MlflowConfig

api/config/config.go

@@ -288,6 +288,7 @@ type GitlabConfig struct {
 	DashboardBranch     string `default:"master"`
 	AlertRepository     string
 	AlertBranch         string `default:"master"`
+	AlertPathPrefix     string
 }
 
 type WardenConfig struct {

api/config/config_test.go

@@ -490,8 +490,9 @@ func TestLoad(t *testing.T) {
 							BaseURL:             "https://test.io/",
 							DashboardRepository: "dashboards/merlin",
 							DashboardBranch:     "master",
-							AlertRepository:     "alerts/merlin",
+							AlertRepository:     "alerts_repository/merlin",
 							AlertBranch:         "master",
+							AlertPathPrefix:     "alerts/merlin",
 						},
 						WardenConfig: WardenConfig{
 							APIHost: "https://test.io/",

api/config/testdata/base-configs-1.yaml

@@ -115,8 +115,9 @@ FeatureToggleConfig:
       BaseURL: https://test.io/
       DashboardRepository: dashboards/merlin
       DashboardBranch: master
-      AlertRepository: alerts/merlin
+      AlertRepository: alerts_repository/merlin
       AlertBranch: master
+      AlertPathPrefix: alerts/merlin
     WardenConfig:
       APIHost: https://test.io/
   ModelDeletionConfig:

api/service/model_endpoint_alert_service.go

@@ -44,6 +44,7 @@ type modelEndpointAlertService struct {
 	dashboardBranch     string
 	alertRepository     string
 	alertBranch         string
+	alertPathPrefix     string
 
 	dashboardBaseURL string
 }
@@ -53,7 +54,7 @@ func NewModelEndpointAlertService(
 	alertStorage storage.AlertStorage,
 	gitlabClient gitlab.Client, wardenClient warden.Client,
 	dashboardRepository, dashboardBranch,
-	alertRepository, alertBranch, dashboardBaseURL string) ModelEndpointAlertService {
+	alertRepository, alertBranch, alertPathPrefix, dashboardBaseURL string) ModelEndpointAlertService {
 	return &modelEndpointAlertService{
 		alertStorage: alertStorage,
 		gitlabClient: gitlabClient,
@@ -63,6 +64,7 @@ func NewModelEndpointAlertService(
 		dashboardBranch:     dashboardBranch,
 		alertRepository:     alertRepository,
 		alertBranch:         alertBranch,
+		alertPathPrefix:     alertPathPrefix,
 
 		dashboardBaseURL: dashboardBaseURL,
 	}
@@ -91,7 +93,7 @@ func (s *modelEndpointAlertService) CreateModelEndpointAlert(user string, alert
 	if err != nil {
 		return nil, err
 	}
-	alertFilename := fmt.Sprintf("alerts/merlin/%s/%s_%s.yaml", alert.Model.Project.Name, alert.Model.Name, alert.EnvironmentName)
+	alertFilename := fmt.Sprintf("%s/%s/%s_%s.yaml", s.alertPathPrefix, alert.Model.Project.Name, alert.Model.Name, alert.EnvironmentName)
 
 	createAlertOpt := gitlab.CreateFileOptions{
 		Repository:    s.alertRepository,
@@ -125,7 +127,7 @@ func (s *modelEndpointAlertService) UpdateModelEndpointAlert(user string, alert
 	if err != nil {
 		return nil, err
 	}
-	alertFilename := fmt.Sprintf("alerts/merlin/%s/%s_%s.yaml", alert.Model.Project.Name, alert.Model.Name, alert.EnvironmentName)
+	alertFilename := fmt.Sprintf("%s/%s/%s_%s.yaml", s.alertPathPrefix, alert.Model.Project.Name, alert.Model.Name, alert.EnvironmentName)
 
 	updateAlertOpt := gitlab.UpdateFileOptions{
 		Repository:    s.alertRepository,