Add mcutie MQTT client implementation and improve library structure

- Integrated `mcutie` library as a core MQTT client for device communication.
- Added support for Home Assistant entities (binary sensor, button) via MQTT.
- Implemented buffer management, async operations, and packet encoding/decoding.
- Introduced structured error handling and device registration features.
- Updated `Cargo.toml` with new dependencies and enabled feature flags for `serde` and `log`.
- Enhanced logging macros with configurable options (`defmt` or `log`).
- Organized codebase into modules (buffer, components, IO, publish, etc.) for better maintainability.

Software/MainBoard/rust/src/mcutie_3_0_0/publish.rs

@@ -0,0 +1,173 @@
+use core::{fmt::Display, future::Future, ops::Deref};
+
+use embedded_io::Write;
+use mqttrs::QoS;
+
+use crate::{io::publish, Error, Payload, Topic, TopicString};
+
+/// A message that can be published to an MQTT broker.
+pub trait Publishable {
+    /// Write this message's topic into the supplied buffer.
+    fn write_topic(&self, buffer: &mut TopicString) -> Result<(), Error>;
+
+    /// Write this message's payload into the supplied buffer.
+    fn write_payload(&self, buffer: &mut Payload) -> Result<(), Error>;
+
+    /// Get this message's QoS level.
+    fn qos(&self) -> QoS {
+        QoS::AtMostOnce
+    }
+
+    /// Whether the broker should retain this message.
+    fn retain(&self) -> bool {
+        false
+    }
+
+    /// Publishes this message to the broker. If the stack has not yet been
+    /// initialized this is likely to panic.
+    fn publish(&self) -> impl Future<Output = Result<(), Error>> {
+        async {
+            let mut topic = TopicString::new();
+            self.write_topic(&mut topic)?;
+
+            let mut payload = Payload::new();
+            self.write_payload(&mut payload)?;
+
+            publish(&topic, &payload, self.qos(), self.retain()).await
+        }
+    }
+}
+
+/// A [`Publishable`] with a raw byte payload.
+pub struct PublishBytes<'a, T, B: AsRef<[u8]>> {
+    pub(crate) topic: &'a Topic<T>,
+    pub(crate) data: B,
+    pub(crate) qos: QoS,
+    pub(crate) retain: bool,
+}
+
+impl<T, B: AsRef<[u8]>> PublishBytes<'_, T, B> {
+    /// Sets the QoS level for this message.
+    pub fn qos(mut self, qos: QoS) -> Self {
+        self.qos = qos;
+        self
+    }
+
+    /// Sets whether the broker should retain this message.
+    pub fn retain(mut self, retain: bool) -> Self {
+        self.retain = retain;
+        self
+    }
+}
+
+impl<'a, T: Deref<Target = str> + 'a, B: AsRef<[u8]>> Publishable for PublishBytes<'a, T, B> {
+    fn write_topic(&self, buffer: &mut TopicString) -> Result<(), Error> {
+        self.topic.to_string(buffer)
+    }
+
+    fn write_payload(&self, buffer: &mut Payload) -> Result<(), Error> {
+        buffer
+            .write_all(self.data.as_ref())
+            .map_err(|_| Error::TooLarge)
+    }
+
+    fn qos(&self) -> QoS {
+        self.qos
+    }
+
+    fn retain(&self) -> bool {
+        self.retain
+    }
+
+    async fn publish(&self) -> Result<(), Error> {
+        let mut topic = TopicString::new();
+        self.write_topic(&mut topic)?;
+
+        publish(&topic, self.data.as_ref(), self.qos(), self.retain()).await
+    }
+}
+
+/// A [`Publishable`] with a payload that implements [`Display`].
+pub struct PublishDisplay<'a, T, D: Display> {
+    pub(crate) topic: &'a Topic<T>,
+    pub(crate) data: D,
+    pub(crate) qos: QoS,
+    pub(crate) retain: bool,
+}
+
+impl<T, D: Display> PublishDisplay<'_, T, D> {
+    /// Sets the QoS level for this message.
+    pub fn qos(mut self, qos: QoS) -> Self {
+        self.qos = qos;
+        self
+    }
+
+    /// Sets whether the broker should retain this message.
+    pub fn retain(mut self, retain: bool) -> Self {
+        self.retain = retain;
+        self
+    }
+}
+
+impl<'a, T: Deref<Target = str> + 'a, D: Display> Publishable for PublishDisplay<'a, T, D> {
+    fn write_topic(&self, buffer: &mut TopicString) -> Result<(), Error> {
+        self.topic.to_string(buffer)
+    }
+
+    fn write_payload(&self, buffer: &mut Payload) -> Result<(), Error> {
+        write!(buffer, "{}", self.data).map_err(|_| Error::TooLarge)
+    }
+
+    fn qos(&self) -> QoS {
+        self.qos
+    }
+
+    fn retain(&self) -> bool {
+        self.retain
+    }
+}
+
+#[cfg(feature = "serde")]
+/// A [`Publishable`] with that serializes a JSON payload.
+pub struct PublishJson<'a, T, D: serde::Serialize> {
+    pub(crate) topic: &'a Topic<T>,
+    pub(crate) data: D,
+    pub(crate) qos: QoS,
+    pub(crate) retain: bool,
+}
+
+#[cfg(feature = "serde")]
+impl<T, D: serde::Serialize> PublishJson<'_, T, D> {
+    /// Sets the QoS level for this message.
+    pub fn qos(mut self, qos: QoS) -> Self {
+        self.qos = qos;
+        self
+    }
+
+    /// Sets whether the broker should retain this message.
+    pub fn retain(mut self, retain: bool) -> Self {
+        self.retain = retain;
+        self
+    }
+}
+
+#[cfg(feature = "serde")]
+impl<'a, T: Deref<Target = str> + 'a, D: serde::Serialize> Publishable for PublishJson<'a, T, D> {
+    fn write_topic(&self, buffer: &mut TopicString) -> Result<(), Error> {
+        self.topic.to_string(buffer)
+    }
+
+    fn write_payload(&self, buffer: &mut Payload) -> Result<(), Error> {
+        buffer
+            .serialize_json(&self.data)
+            .map_err(|_| Error::TooLarge)
+    }
+
+    fn qos(&self) -> QoS {
+        self.qos
+    }
+
+    fn retain(&self) -> bool {
+        self.retain
+    }
+}