fix: improve "upstream/latest" release trains (#2034)

Previously the release train to "latest" would consider all apps.
Now it only considers apps that exist (have a release) in the target
env.

Ref: SRX-LEIHOZ

services/cd-service/pkg/repository/repository.go

@@ -2079,6 +2079,9 @@ func (s *State) GetEnvironmentApplicationsFromDB(ctx context.Context, transactio
 	if err != nil {
 		return nil, err
 	}
+	if envInfo == nil {
+		return nil, fmt.Errorf("environment %s not found", environment)
+	}
 	if envInfo.Applications == nil {
 		return make([]string, 0), nil
 	}

services/cd-service/pkg/repository/transformer.go

@@ -3388,7 +3388,7 @@ func getOverrideVersions(ctx context.Context, transaction *sql.Tx, commitHash, u
 	return resp, nil
 }
 
-func (c *ReleaseTrain) getUpstreamLatestApp(ctx context.Context, transaction *sql.Tx, upstreamLatest bool, state *State, upstreamEnvName, source, commitHash string) (apps []string, appVersions []Overview, err error) {
+func (c *ReleaseTrain) getUpstreamLatestApp(ctx context.Context, transaction *sql.Tx, upstreamLatest bool, state *State, upstreamEnvName, source, commitHash string, targetEnv string) (apps []string, appVersions []Overview, err error) {
 	if commitHash != "" {
 		appVersions, err := getOverrideVersions(ctx, transaction, c.CommitHash, upstreamEnvName, c.Repo)
 		if err != nil {
@@ -3409,7 +3409,9 @@ func (c *ReleaseTrain) getUpstreamLatestApp(ctx context.Context, transaction *sq
 		return apps, appVersions, nil
 	}
 	if upstreamLatest {
-		apps, err = state.GetApplications(ctx, transaction)
+		// For "upstreamlatest" we cannot get the source environment, because it's not a real environment
+		// but since we only care about the names of the apps, we can just get the apps for the target env.
+		apps, err = state.GetEnvironmentApplications(ctx, transaction, targetEnv)
 		if err != nil {
 			return nil, nil, grpc.PublicError(ctx, fmt.Errorf("could not get all applications for %q: %w", source, err))
 		}
@@ -3710,7 +3712,7 @@ func (c *envReleaseTrain) prognosis(
 		source = "latest"
 	}
 
-	apps, overrideVersions, err := c.Parent.getUpstreamLatestApp(ctx, transaction, upstreamLatest, state, upstreamEnvName, source, c.Parent.CommitHash)
+	apps, overrideVersions, err := c.Parent.getUpstreamLatestApp(ctx, transaction, upstreamLatest, state, upstreamEnvName, source, c.Parent.CommitHash, c.Env)
 	if err != nil {
 		return ReleaseTrainEnvironmentPrognosis{
 			SkipCause:     nil,