feat: add meta plugin with file and none implementations

src/meta_plugin/none.rs

@@ -0,0 +1,43 @@
+use anyhow::Result;
+use log::*;
+use std::io::{self, Write};
+
+#[derive(Debug, Eq, PartialEq, Clone, Default)]
+pub struct MetaPluginNone {}
+
+impl MetaPluginNone {
+    pub fn new() -> MetaPluginNone {
+        MetaPluginNone {}
+    }
+}
+
+impl MetaPlugin for MetaPluginNone {
+    fn create(&self) -> Result<Box<dyn Write>> {
+        Ok(Box::new(DummyWriter::new()))
+    }
+
+    fn finalize(&mut self) -> io::Result<String> {
+        Ok("none".to_string())
+    }
+
+    fn update(&mut self, _data: &[u8]) {}
+}
+
+// Dummy writer that implements Write for the none meta plugin
+struct DummyWriter;
+
+impl DummyWriter {
+    fn new() -> Self {
+        DummyWriter
+    }
+}
+
+impl Write for DummyWriter {
+    fn write(&mut self, _buf: &[u8]) -> io::Result<usize> {
+        Ok(0)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}