Add financial transaction classes

Fossil/src/main/java/me/totalfreedom/fossil/economy/SimpleCompletedTransaction.java

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+package me.totalfreedom.fossil.economy;
+
+import me.totalfreedom.economy.CompletedTransaction;
+import me.totalfreedom.economy.Transaction;
+import me.totalfreedom.economy.TransactionResult;
+
+public class SimpleCompletedTransaction implements CompletedTransaction
+{
+    private final Transaction transaction;
+    private final TransactionResult transactionResult;
+
+    public SimpleCompletedTransaction(Transaction transaction, TransactionResult transactionResult)
+    {
+        this.transaction = transaction.copy();
+        this.transactionResult = transactionResult;
+    }
+
+
+    @Override
+    public Transaction getTransaction()
+    {
+        return transaction.copy();
+    }
+
+    @Override
+    public TransactionResult getResult()
+    {
+        return transactionResult;
+    }
+}

Fossil/src/main/java/me/totalfreedom/fossil/economy/SimpleTransaction.java

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+package me.totalfreedom.fossil.economy;
+
+import me.totalfreedom.economy.EconomicEntity;
+import me.totalfreedom.economy.Transaction;
+
+import java.util.concurrent.atomic.AtomicLong;
+
+public class SimpleTransaction implements Transaction
+{
+    private final EconomicEntity source;
+    private final EconomicEntity destination;
+    private final AtomicLong transferAmount;
+
+    public SimpleTransaction(EconomicEntity source, EconomicEntity destination, long transferAmount)
+    {
+        this.source = source;
+        this.destination = destination;
+        this.transferAmount = new AtomicLong(transferAmount);
+    }
+
+    @Override
+    public Transaction copy()
+    {
+        return new SimpleTransaction(source, destination, transferAmount.get());
+    }
+
+    @Override
+    public EconomicEntity getSource()
+    {
+        return this.source;
+    }
+
+    @Override
+    public EconomicEntity getDestination()
+    {
+        return this.destination;
+    }
+
+    @Override
+    public long getTransferAmount()
+    {
+        return this.transferAmount.get();
+    }
+
+    @Override
+    public long addBalance(long amount)
+    {
+        return this.transferAmount.addAndGet(amount);
+    }
+
+    @Override
+    public long removeBalance(long amount)
+    {
+        return this.addBalance(-amount);
+    }
+}

Fossil/src/main/java/me/totalfreedom/fossil/economy/SimpleTransactionResult.java

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+package me.totalfreedom.fossil.economy;
+
+import me.totalfreedom.economy.TransactionResult;
+import net.kyori.adventure.text.Component;
+import net.kyori.adventure.text.format.NamedTextColor;
+
+public class SimpleTransactionResult implements TransactionResult
+{
+    private final String message;
+    private final Component component;
+    private final boolean successful;
+
+    public SimpleTransactionResult(String message, boolean successful)
+    {
+        this(message, Component.text(message, successful ? NamedTextColor.GREEN : NamedTextColor.RED), successful);
+    }
+
+    public SimpleTransactionResult(String message, Component component, boolean successful)
+    {
+        this.message = message;
+        this.component = component;
+        this.successful = successful;
+    }
+
+    @Override
+    public String getMessage()
+    {
+        return message;
+    }
+
+    @Override
+    public boolean isSuccessful()
+    {
+        return successful;
+    }
+
+    @Override
+    public Component getComponent()
+    {
+        return component;
+    }
+}

Patchwork/src/main/java/me/totalfreedom/economy/CompletedTransaction.java

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+package me.totalfreedom.economy;
+
+public interface CompletedTransaction
+{
+    Transaction getTransaction();
+
+    TransactionResult getResult();
+}

Patchwork/src/main/java/me/totalfreedom/economy/Transaction.java

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+package me.totalfreedom.economy;
+
+public interface Transaction
+{
+    Transaction copy();
+
+    EconomicEntity getSource();
+
+    EconomicEntity getDestination();
+
+    long getTransferAmount();
+
+    long addBalance(final long amount);
+
+    long removeBalance(final long amount);
+}

Patchwork/src/main/java/me/totalfreedom/economy/TransactionResult.java

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+package me.totalfreedom.economy;
+
+import net.kyori.adventure.text.Component;
+
+public interface TransactionResult
+{
+    String getMessage();
+
+    boolean isSuccessful();
+
+    Component getComponent();
+}