various fixes and updates for satrs-core

1. Fix pools integration test to avoid occasional deadlocks
2. tmtc module: The `CcsdsPacketHandler` and `PusServiceProvider`
   do not require a send bound anymore. However, these traits now
   have an extension trait called `Sendable<DefaultName>` which requires
   the trait + Send. A blanket implementation is provided. The helper
   structs like `PusDistributor` and `CcsdsDistributor` require
   the new Sendable trait version to allow more ergnomic usage
   with threads.

satrs-core/src/tmtc/ccsds_distrib.rs

@@ -99,7 +99,7 @@ use spacepackets::{ByteConversionError, CcsdsPacket, SizeMissmatch, SpHeader};
 /// This trait automatically implements the [downcast_rs::Downcast] to allow a more convenient API
 /// to cast trait objects back to their concrete type after the handler was passed to the
 /// distributor.
-pub trait CcsdsPacketHandler: Downcast + Send {
+pub trait CcsdsPacketHandler: Downcast {
     type Error;
 
     fn valid_apids(&self) -> &'static [u16];
@@ -114,12 +114,21 @@ pub trait CcsdsPacketHandler: Downcast + Send {
 
 downcast_rs::impl_downcast!(CcsdsPacketHandler assoc Error);
 
+pub trait SendableCcsdsPacketHandler: CcsdsPacketHandler + Send {}
+
+impl<T: CcsdsPacketHandler + Send> SendableCcsdsPacketHandler for T {}
+
+downcast_rs::impl_downcast!(SendableCcsdsPacketHandler assoc Error);
+
 /// The CCSDS distributor dispatches received CCSDS packets to a user provided packet handler.
+///
+/// The passed APID handler is required to be [Send]able to allow more ergonomic usage with
+/// threads.
 pub struct CcsdsDistributor<E> {
     /// User provided APID handler stored as a generic trait object.
     /// It can be cast back to the original concrete type using the [Self::apid_handler_ref] or
     /// the [Self::apid_handler_mut] method.
-    pub apid_handler: Box<dyn CcsdsPacketHandler<Error = E>>,
+    pub apid_handler: Box<dyn SendableCcsdsPacketHandler<Error = E>>,
 }
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
@@ -155,20 +164,20 @@ impl<E: 'static> ReceivesTcCore for CcsdsDistributor<E> {
 }
 
 impl<E: 'static> CcsdsDistributor<E> {
-    pub fn new(apid_handler: Box<dyn CcsdsPacketHandler<Error = E>>) -> Self {
+    pub fn new(apid_handler: Box<dyn SendableCcsdsPacketHandler<Error = E>>) -> Self {
         CcsdsDistributor { apid_handler }
     }
 
     /// This function can be used to retrieve a reference to the concrete instance of the APID
     /// handler after it was passed to the distributor. See the
     /// [module documentation][crate::tmtc::ccsds_distrib] for an fsrc-example.
-    pub fn apid_handler_ref<T: CcsdsPacketHandler<Error = E>>(&self) -> Option<&T> {
+    pub fn apid_handler_ref<T: SendableCcsdsPacketHandler<Error = E>>(&self) -> Option<&T> {
         self.apid_handler.downcast_ref::<T>()
     }
 
     /// This function can be used to retrieve a mutable reference to the concrete instance of the
     /// APID handler after it was passed to the distributor.
-    pub fn apid_handler_mut<T: CcsdsPacketHandler<Error = E>>(&mut self) -> Option<&mut T> {
+    pub fn apid_handler_mut<T: SendableCcsdsPacketHandler<Error = E>>(&mut self) -> Option<&mut T> {
         self.apid_handler.downcast_mut::<T>()
     }