[fix lint warnings: NFTs pallet] fix clippy::missing_docs_in_private_items warnings (#14610)

* add docs for impl_codec_bitflags

* add missing docs for type aliases

* add docs to transfer module

* add docs for settings module

* add docs to roles module

* add docs to metadata module

* add docs to migration module

* add missing docs to feature library

* methods not functions

* add docs to lock module

* add docs to attributes module

* add docs to create_delete_item module

* add docs for create_delete_collection module

* add docs to buy_sell module

* add missing doc for buy_sell module

* add docs to atomic_swap module

* add docs to atomic_swap module

* add docs for approvals module

* run cargo fmt

* Fix issues with multi-line comments

* Apply suggestions from code review

Co-authored-by: Jegor Sidorenko <5252494+jsidorenko@users.noreply.github.com>

* update from review

* fmt

* update from review

* remove bitflag example

* ".git/.scripts/commands/fmt/fmt.sh"

* Apply suggestions from code review

Co-authored-by: Squirrel <gilescope@gmail.com>

* add note about pallet features

---------

Co-authored-by: Jegor Sidorenko <jegor@parity.io>
Co-authored-by: Jegor Sidorenko <5252494+jsidorenko@users.noreply.github.com>
Co-authored-by: parity-processbot <>
Co-authored-by: Squirrel <gilescope@gmail.com>

substrate/frame/nfts/src/features/metadata.rs

@@ -15,11 +15,29 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+//! This module contains helper methods to configure the metadata of collections and items.
+
 use crate::*;
 use frame_support::pallet_prelude::*;
 
 impl<T: Config<I>, I: 'static> Pallet<T, I> {
-	/// Note: if `maybe_depositor` is None, that means the depositor will be a collection's owner
+	/// Sets the metadata for a specific item within a collection.
+	///
+	/// - `maybe_check_origin`: An optional account ID that is allowed to set the metadata. If
+	///   `None`, it's considered the root account.
+	/// - `collection`: The ID of the collection to which the item belongs.
+	/// - `item`: The ID of the item to set the metadata for.
+	/// - `data`: The metadata to set for the item.
+	/// - `maybe_depositor`: An optional account ID that will provide the deposit for the metadata.
+	///   If `None`, the collection's owner provides the deposit.
+	///
+	/// Emits `ItemMetadataSet` event upon successful setting of the metadata.
+	/// Returns `Ok(())` on success, or one of the following dispatch errors:
+	/// - `UnknownCollection`: The specified collection does not exist.
+	/// - `UnknownItem`: The specified item does not exist within the collection.
+	/// - `LockedItemMetadata`: The metadata for the item is locked and cannot be modified.
+	/// - `NoPermission`: The caller does not have the required permission to set the metadata.
+	/// - `DepositExceeded`: The deposit amount exceeds the maximum allowed value.
 	pub(crate) fn do_set_item_metadata(
 		maybe_check_origin: Option<T::AccountId>,
 		collection: T::CollectionId,
@@ -91,6 +109,19 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 		})
 	}
 
+	/// Clears the metadata for a specific item within a collection.
+	///
+	/// - `maybe_check_origin`: An optional account ID that is allowed to clear the metadata. If
+	///   `None`, it's considered the root account.
+	/// - `collection`: The ID of the collection to which the item belongs.
+	/// - `item`: The ID of the item for which to clear the metadata.
+	///
+	/// Emits `ItemMetadataCleared` event upon successful clearing of the metadata.
+	/// Returns `Ok(())` on success, or one of the following dispatch errors:
+	/// - `UnknownCollection`: The specified collection does not exist.
+	/// - `MetadataNotFound`: The metadata for the specified item was not found.
+	/// - `LockedItemMetadata`: The metadata for the item is locked and cannot be modified.
+	/// - `NoPermission`: The caller does not have the required permission to clear the metadata.
 	pub(crate) fn do_clear_item_metadata(
 		maybe_check_origin: Option<T::AccountId>,
 		collection: T::CollectionId,
@@ -131,6 +162,19 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 		Ok(())
 	}
 
+	/// Sets the metadata for a specific collection.
+	///
+	/// - `maybe_check_origin`: An optional account ID that is allowed to set the collection
+	///   metadata. If `None`, it's considered the root account.
+	/// - `collection`: The ID of the collection for which to set the metadata.
+	/// - `data`: The metadata to set for the collection.
+	///
+	/// Emits `CollectionMetadataSet` event upon successful setting of the metadata.
+	/// Returns `Ok(())` on success, or one of the following dispatch errors:
+	/// - `UnknownCollection`: The specified collection does not exist.
+	/// - `LockedCollectionMetadata`: The metadata for the collection is locked and cannot be
+	///   modified.
+	/// - `NoPermission`: The caller does not have the required permission to set the metadata.
 	pub(crate) fn do_set_collection_metadata(
 		maybe_check_origin: Option<T::AccountId>,
 		collection: T::CollectionId,
@@ -179,6 +223,19 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 		})
 	}
 
+	/// Clears the metadata for a specific collection.
+	///
+	/// - `maybe_check_origin`: An optional account ID that is allowed to clear the collection
+	///   metadata. If `None`, it's considered the root account.
+	/// - `collection`: The ID of the collection for which to clear the metadata.
+	///
+	/// Emits `CollectionMetadataCleared` event upon successful clearing of the metadata.
+	/// Returns `Ok(())` on success, or one of the following dispatch errors:
+	/// - `UnknownCollection`: The specified collection does not exist.
+	/// - `MetadataNotFound`: The metadata for the collection was not found.
+	/// - `LockedCollectionMetadata`: The metadata for the collection is locked and cannot be
+	///   modified.
+	/// - `NoPermission`: The caller does not have the required permission to clear the metadata.
 	pub(crate) fn do_clear_collection_metadata(
 		maybe_check_origin: Option<T::AccountId>,
 		collection: T::CollectionId,