Move FoundSrvs::into_stream into feature "stream"

This function (and only this function) depends on the `futures` create,
which itself requires over a dozen other dependencies.

Move the function into its own feature, "stream". This allows enabling
the "resolv" feature without the `futures` dependency tree, which
substantially reduces unnecessary dependencies.

Cargo.toml

@@ -41,12 +41,13 @@ default     = ["std", "rand"]
 bytes       = ["dep:bytes", "octseq/bytes"]
 heapless    = ["dep:heapless", "octseq/heapless"]
 interop     = ["bytes", "ring"]
-resolv      = ["bytes", "futures", "smallvec", "std", "tokio", "libc", "rand"]
+resolv      = ["bytes", "smallvec", "std", "tokio", "libc", "rand"]
 resolv-sync = ["resolv", "tokio/rt"]
 serde       = ["dep:serde", "octseq/serde"]
 sign        = ["std"]
 smallvec    = ["dep:smallvec", "octseq/smallvec"]
 std         = []
+stream      = ["futures"]
 tsig        = ["bytes", "ring", "smallvec"]
 validate    = ["std", "ring"]
 zonefile    = ["bytes", "std"]

Changelog.md

@@ -4,6 +4,9 @@
 
 Breaking changes
 
+* The `FoundSrvs::into_stream` function now requires enabling the `stream`
+  feature.
+
 New
 
 Bug fixes

src/resolv/lookup/srv.rs

@@ -8,14 +8,15 @@ use crate::base::wire::ParseError;
 use crate::rdata::{Aaaa, Srv, A};
 use crate::resolv::resolver::Resolver;
 use core::fmt;
-use futures::stream;
-use futures::stream::{Stream, StreamExt};
 use octseq::octets::Octets;
 use rand::distributions::{Distribution, Uniform};
 use std::net::{IpAddr, SocketAddr};
 use std::vec::Vec;
 use std::{io, mem, ops};
 
+#[cfg(feature = "stream")]
+use futures::stream::{self, Stream, StreamExt};
+
 // Look up SRV record. Three outcomes:
 //
 // *  at least one SRV record with a regular target,
@@ -101,6 +102,7 @@ impl FoundSrvs {
     /// pass in a double reference since [`Resolver`] is implemented for a
     /// reference to it and this method requires a reference to that impl
     /// being passed. This quirk will be fixed in future versions.
+    #[cfg(feature = "stream")]
     pub fn into_stream<R: Resolver>(
         self,
         resolver: &R,