Fix bugs related to templates in Description

Challenges with {{url}} or {{lookup}} template tags in the Description
field will no longer fail validation.

These templates will also be properly rendered when using `cmgr playtest`.

cmd/cmgr/playtest.go

@@ -98,10 +98,21 @@ func launchPortal(mgr *cmgr.Manager, iface string, port int, cid cmgr.ChallengeI
 
 		w.Write([]byte(fmt.Sprintf(`<h1>%s</h1>`, cMeta.Name)))
 
-		w.Write([]byte(fmt.Sprintf(`<h2>Description</h2><p>%s</p>`, cMeta.Description)))
+		artifactUrl := fmt.Sprintf("http://%s:%d/artifact/$1", iface, port)
+
+		description := cMeta.Description
+		description = urlRe.ReplaceAllString(description, artifactUrl)
+		for lookupRe.MatchString(description) {
+			match := lookupRe.FindStringSubmatch(description)
+			description = strings.ReplaceAll(
+				description,
+				match[0],
+				fmt.Sprintf("%s", bMeta.LookupData[match[1]]))
+		}
+
+		w.Write([]byte(fmt.Sprintf(`<h2>Description</h2><p>%s</p>`, description)))
 
 		details := cMeta.Details
-		artifactUrl := fmt.Sprintf("http://%s:%d/artifact/$1", iface, port)
 		details = urlRe.ReplaceAllString(details, artifactUrl)
 		details = serverRe.ReplaceAllString(details, iface)
 		details = httpBaseRe.ReplaceAllString(details, fmt.Sprintf("http://%s", iface))

cmgr/loader.go

@@ -304,8 +304,13 @@ func (m *Manager) validateMetadata(md *ChallengeMetadata) error {
 		return s, err
 	}
 
-	// Validate (& lift) Details
-	res, err := normalizeAndCheckTemplated(md.Details)
+	res, err := normalizeAndCheckTemplated(md.Description)
+	if err != nil {
+		lastErr = err
+	}
+	md.Description = res
+
+	res, err = normalizeAndCheckTemplated(md.Details)
 	if err != nil {
 		lastErr = err
 	}
@@ -447,8 +452,12 @@ func (m *Manager) validateBuild(cMeta *ChallengeMetadata, md *BuildMetadata, fil
 		return err
 	}
 
-	// Validate (& lift) Details
-	err := checkTemplated(cMeta.Details)
+	// Validate templated fields
+	err := checkTemplated(cMeta.Description)
+	detailsErr := checkTemplated(cMeta.Details)
+	if detailsErr != nil {
+		err = detailsErr
+	}
 
 	for _, hint := range cMeta.Hints {
 		tmpErr := checkTemplated(hint)