radicle: fix build when schemars feature is not enabled — heartwood

Commit b608a788 (cli: rad config schema emits JSON Schema, 2025-04-28) added a feature flag that enables the “schemars” optional dependency.

Crate radicle-node doesn’t use this feature. Crate radicle fails to compile when the feature is disabled. This is reproducible with “flake check”. Fix it.

Note that a “cargo build” of the entire workspace doesn’t fail, because the feature is enabled due to “unification”, since “radicle-cli” does use this feature. From https://doc.rust-lang.org/cargo/reference/resolver.html#features:

When building multiple packages in a workspace (such as with –workspace or multiple -p flags), the features [of the dependencies] of all of those packages are unified. If you have a circumstance where you want to avoid that unification for different workspace members, you will need to build them via separate cargo invocations.

 )]
 pub struct ConnectAddress(
     #[serde(with = "crate::serde_ext::string")]
     #[schemars(
     #[cfg_attr(feature = "schemars", schemars(
         with = "String",
         regex(pattern = r"^.+@.+:((6553[0-5])|(655[0-2][0-9])|(65[0-4][0-9]{2})|(6[0-4][0-9]{3})|([1-5][0-9]{4})|([0-5]{0,5})|([0-9]{1,4}))$"),
         extend("examples" = [

             "z6MknSLrJoTcukLrE435hVNQT4JUhbvWLX4kUzqkEStBU8Vi@seed.example.com:8776",
             "z6MkkfM3tPXNPrPevKr3uSiQtHPuwnNhu2yUVjgd2jXVsVz5@192.0.2.0:31337",
         ]),
     )]
     ))]
     PeerAddr<NodeId, Address>,
 );

 use crate::prelude::RepoId;
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
 use std::collections::HashSet;

 /// Pinned content. This can be used to pin certain content when
 /// listing, e.g. pin repositories on a web client.
 #[derive(Clone, Debug, Default, Serialize, Deserialize, JsonSchema)]
 #[derive(Clone, Debug, Default, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 #[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
 pub struct Pinned {
     /// Pinned repositories.
     pub repositories: HashSet<RepoId>,