Relax genesis config to not require `Default` impl (#1221)

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

substrate/frame/support/src/genesis_builder_helper.rs

@@ -25,7 +25,10 @@ use sp_runtime::format_runtime_string;
 
 /// Get the default `GenesisConfig` as a JSON blob. For more info refer to
 /// [`sp_genesis_builder::GenesisBuilder::create_default_config`]
-pub fn create_default_config<GC: BuildGenesisConfig>() -> sp_std::vec::Vec<u8> {
+pub fn create_default_config<GC>() -> sp_std::vec::Vec<u8>
+where
+	GC: BuildGenesisConfig + Default,
+{
 	serde_json::to_string(&GC::default())
 		.expect("serialization to json is expected to work. qed.")
 		.into_bytes()

substrate/frame/support/src/traits/hooks.rs

@@ -442,7 +442,7 @@ pub trait Hooks<BlockNumber> {
 /// A trait to define the build function of a genesis config for both runtime and pallets.
 ///
 /// Replaces deprecated [`GenesisBuild<T,I>`].
-pub trait BuildGenesisConfig: Default + sp_runtime::traits::MaybeSerializeDeserialize {
+pub trait BuildGenesisConfig: sp_runtime::traits::MaybeSerializeDeserialize {
 	/// The build function puts initial `GenesisConfig` keys/values pairs into the storage.
 	fn build(&self);
 }
@@ -452,7 +452,7 @@ pub trait BuildGenesisConfig: Default + sp_runtime::traits::MaybeSerializeDeseri
 #[deprecated(
 	note = "GenesisBuild is planned to be removed in December 2023. Use BuildGenesisConfig instead of it."
 )]
-pub trait GenesisBuild<T, I = ()>: Default + sp_runtime::traits::MaybeSerializeDeserialize {
+pub trait GenesisBuild<T, I = ()>: sp_runtime::traits::MaybeSerializeDeserialize {
 	/// The build function is called within an externalities allowing storage APIs.
 	/// Thus one can write to storage using regular pallet storages.
 	fn build(&self);