Return error when unable to read configuration

Prior when the configuration was not successfully fetched, the error was
only logged but execution continued. Not fetching the configuration is
an unrecoverable error that should result in upstream failure.

Instead return the error to caller and let them log it.

internal/pkg/githubapi/github.go

@@ -189,7 +189,7 @@ func handleShowPlanPREvent(ctx context.Context, ghPrClientDetails GhPrClientDeta
 	defaultBranch, _ := ghPrClientDetails.GetDefaultBranch()
 	config, err := GetInRepoConfig(ghPrClientDetails, defaultBranch)
 	if err != nil {
-		ghPrClientDetails.PrLogger.Infof("Couldn't get Telefonistka in-repo configuration: %v", err)
+		return fmt.Errorf("get in-repo configuration: %w", err)
 	}
 	promotions, _ := GeneratePromotionPlan(ghPrClientDetails, config, *eventPayload.PullRequest.Head.Ref)
 	commentPlanInPR(ghPrClientDetails, promotions)
@@ -205,7 +205,7 @@ func handleChangedPREvent(ctx context.Context, mainGithubClientPair GhClientPair
 	defaultBranch, _ := ghPrClientDetails.GetDefaultBranch()
 	config, err := GetInRepoConfig(ghPrClientDetails, defaultBranch)
 	if err != nil {
-		ghPrClientDetails.PrLogger.Infof("Couldn't get Telefonistka in-repo configuration: %v", err)
+		return fmt.Errorf("get in-repo configuration: %w", err)
 	}
 	if config.Argocd.CommentDiffonPR {
 		componentPathList, err := generateListOfChangedComponentPaths(ghPrClientDetails, config)