gnu: Add rust-signature-2.

* gnu/packages/crates-io.scm (rust-signature-2): New variable.
(rust-signature-1): Inherit from rust-signature-2.

gnu/packages/crates-io.scm

@@ -57625,8 +57625,37 @@ words, like Python's shlex.")
        (("rust-signal-hook" ,rust-signal-hook-0.1)
         ("rust-version-sync" ,rust-version-sync-0.8))))))
 
+(define-public rust-signature-2
+  (package
+    (name "rust-signature")
+    (version "2.1.0")
+    (source (origin
+              (method url-fetch)
+              (uri (crate-uri "signature" version))
+              (file-name (string-append name "-" version ".tar.gz"))
+              (sha256
+               (base32
+                "00457czdia5gvll3a1vzf2ffsdpgcz2dz0h56z7zk28nsbp8h5sy"))))
+    (build-system cargo-build-system)
+    (arguments
+     `(#:cargo-inputs
+       (("rust-digest" ,rust-digest-0.10)
+        ("rust-rand-core" ,rust-rand-core-0.6)
+        ("rust-signature-derive" ,rust-signature-derive-2))
+       #:cargo-development-inputs
+       (("rust-hex-literal" ,rust-hex-literal-0.3)
+        ("rust-sha2" ,rust-sha2-0.10))))
+    (home-page "https://github.com/RustCrypto/traits/tree/master/signature")
+    (synopsis
+     "Traits for cryptographic signature algorithms (e.g. ECDSA, Ed25519)")
+    (description
+     "This package contains traits which provide generic, object-safe APIs
+for generating and verifying digital signatures.")
+    (license (list license:asl2.0 license:expat))))
+
 (define-public rust-signature-1
   (package
+    (inherit rust-signature-2)
     (name "rust-signature")
     (version "1.5.0")
     (source
@@ -57636,20 +57665,12 @@ words, like Python's shlex.")
        (file-name (string-append name "-" version ".tar.gz"))
        (sha256
         (base32 "1r4x94n6ibdd1f85cwmvi29jvyyf1l379n9yybb7jlg9lv0wcm7h"))))
-    (build-system cargo-build-system)
     (arguments
      `(#:skip-build? #t
        #:cargo-inputs
        (("rust-digest" ,rust-digest-0.10)
         ("rust-rand-core" ,rust-rand-core-0.6)
-        ("rust-signature-derive" ,rust-signature-derive-1))))
-    (home-page "")
-    (synopsis "Traits for cryptographic signature algorithms (e.g. ECDSA,
-Ed25519)")
-    (description
-     "This package contains traits which provide generic, object-safe APIs
-for generating and verifying digital signatures.")
-    (license (list license:asl2.0 license:expat))))
+        ("rust-signature-derive" ,rust-signature-derive-1))))))
 
 (define-public rust-signature-derive-2
   (package