Add rand feature

Currently we activate the "bitcoin/rand-std" feature unconditionally
in `json`. Some users may not wish to use the bitcoin "rand" feature.

Add a "rand" feature to `json` and `client` and use it to activate
"rand-std" in `bitcoin`.

The crates currently have no features, this is the first. In order to be
less of a breaking change also add a "default" feature and enable "rand"
from "default".

client/Cargo.toml

@@ -18,6 +18,10 @@ edition = "2018"
 name = "bitcoincore_rpc"
 path = "src/lib.rs"
 
+[features]
+default = ["rand"]
+rand = ["bitcoincore-rpc-json/rand"]
+
 [dependencies]
 bitcoincore-rpc-json = { version = "0.18.0", path = "../json" }
 

integration_test/Cargo.toml

@@ -5,7 +5,7 @@ authors = ["Steven Roose <[email protected]>"]
 edition = "2018"
 
 [dependencies]
-bitcoincore-rpc = { path = "../client" }
+bitcoincore-rpc = { path = "../client", features = ["rand"] }
 bitcoin = { version = "0.32.0", features = ["serde", "rand"] }
 lazy_static = "1.4.0"
 log = "0.4"

json/Cargo.toml

@@ -19,8 +19,12 @@ rust-version = "1.56.1"
 name = "bitcoincore_rpc_json"
 path = "src/lib.rs"
 
+[features]
+default = ["rand"]
+rand = ["bitcoin/rand-std"]
+
 [dependencies]
 serde = { version = "1", features = [ "derive" ] }
 serde_json = "1"
 
-bitcoin = { version = "0.32.0", features = ["serde", "rand-std"] }
+bitcoin = { version = "0.32.0", features = ["serde"] }