Add some logging for modelconfig problems

cmd/frontend/internal/modelconfig/init.go

@@ -158,6 +158,7 @@ func (m *manager) applyNewSiteConfig(latestSiteConfig schema.SiteConfiguration)
 	m.builder.siteConfigData = latestSiteModelConfiguration
 	updatedConfig, err := m.builder.build()
 	if err != nil {
+		m.logger.Error("error calculating modelconfig", log.Error(err))
 		return nil, err
 	}
 

cmd/frontend/internal/modelconfig/siteconfig.go

@@ -26,6 +26,11 @@ func maybeGetSiteModelConfiguration(logger log.Logger, siteConfig schema.SiteCon
 		logger.Info("converting completions configuration data", log.String("apiProvider", string(compConfig.Provider)))
 		return convertCompletionsConfig(compConfig)
 	}
+
+	// There are some situations where conf.GetCompletionsConfig will return nil, even though there
+	// is some configuration data put in the site config. e.g. if Cody isn't enabled on the Sourcegraph
+	// license, or there are some validation errors such as a required endpoint not being set.
+	logger.Warn("no site model configuration found")
 	return nil, nil
 }