start adding CFDP state machines

satrs-core/src/cfdp/mod.rs

@@ -0,0 +1,25 @@
+pub mod dest;
+
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub enum TransactionStep {
+    Idle = 0,
+    TransactionStart = 1,
+    ReceivingFileDataPdus = 2,
+    SendingAckPdu = 3,
+    TransferCompletion = 4,
+    SendingFinishedPdu = 5
+}
+
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub enum State {
+    Idle = 0,
+    BusyClass1Nacked = 2,
+    BusyClass2Acked = 3,
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn basic_test() {
+    }
+}