feat: ensure referenced images get updated by dependabot

Dokku uses a few external images for various bits of functionality, but these must be manually updated every so often due to being referenced in code.

By moving the references to Dockerfiles, we can take advantage of dependabot to issue automatic PRs when they are out of date.

plugins/logs/functions.go

@@ -121,6 +121,17 @@ func startVectorContainer(vectorImage string) error {
 	return nil
 }
 
+func getComputedVectorImage() string {
+	return common.PropertyGetDefault("logs", "--global", "vector-image", getDefaultVectorImage())
+}
+
+// getDefaultVectorImage returns the default image used for the vector container
+func getDefaultVectorImage() string {
+	contents := strings.TrimSpace(VectorDockerfile)
+	parts := strings.SplitN(contents, " ", 2)
+	return parts[1]
+}
+
 func stopVectorContainer() error {
 	if !common.IsComposeInstalled() {
 		return errors.New("Required docker compose plugin is not installed")
@@ -159,7 +170,7 @@ func stopVectorContainer() error {
 	data := vectorTemplateData{
 		DokkuLibRoot: dokkuLibRoot,
 		DokkuLogsDir: dokkuLogsDir,
-		VectorImage:  VectorImage,
+		VectorImage:  getComputedVectorImage(),
 	}
 
 	if err := tmpl.Execute(tmpFile, data); err != nil {