Add signature providers

Requires: common-ci-configuration!75 (merged)

ts/packages/signers-keychain/src/index.ts

+import type { IOnlineSignatureProvider, ITransaction, TAccountName, TRole } from "@hiveio/wax";
+import { WaxError } from "@hiveio/wax";
+
+import { KeychainKeyTypes, KeychainSDK } from "keychain-sdk";
+
+const keychain = new KeychainSDK(window);
+
+const mapRoles: Record<TRole, KeychainKeyTypes | undefined> = {
+  active: KeychainKeyTypes.active,
+  posting: KeychainKeyTypes.posting,
+  owner: undefined,
+  memo: KeychainKeyTypes.memo
+};
+
+export class WaxKeychainProviderError extends WaxError {}
+
+/**
+ * Wax transaction signature provider using the Keychain SDK.
+ *
+ * @example
+ * ```
+ * const provider = KeychainProvider.for("myaccount", "active");
+ *
+ * // Create a transaction using the Wax Hive chain instance
+ * const tx = await chain.createTransaction();
+ *
+ * // Perform some operations, e.g. pushing operations...
+ *
+ * // Sign the transaction
+ * await tx.sign(provider);
+ *
+ * // broadcast
+ * await chain.broadcast(tx);
+ * ```
+ */
+class KeychainProvider implements IOnlineSignatureProvider {
+  private readonly role: KeychainKeyTypes;
+
+  private constructor(
+    private readonly accountName: TAccountName,
+    role: TRole
+  ) {
+    if (!mapRoles[role])
+      throw new WaxKeychainProviderError(`Role ${role} is not supported by the Wax signature provider: ${KeychainProvider.name}`);
+
+    this.role = mapRoles[role];
+  }
+
+  public static for(accountName: TAccountName, role: TRole): KeychainProvider {
+    return new KeychainProvider(accountName, role);
+  }
+
+  public async signTransaction(transaction: ITransaction): Promise<void> {
+    const data = await keychain.signTx({
+      method: mapRoles[this.role]!,
+      username: this.accountName,
+      tx: JSON.parse(transaction.toLegacyApi())
+    });
+
+    for(const sig of data.result.signatures)
+      transaction.sign(sig);
+  }
+}
+
+export default KeychainProvider;