refactor(core-preference): add AccountKeyGenerator to legacy module

package net.thunderbird.feature.account.storage.legacy

import net.thunderbird.feature.account.AccountId

/**

 * Generates keys for account storage.

 */

class AccountKeyGenerator(

    private val id: AccountId,

) {

    /**

     * Creates a key by combining account ID with the specified key.

     *

     * @param key The key to combine with the account ID.

     */

    fun create(key: String): String {

        return "${id.asRaw()}.$key"

    }

}