Introduce Mining interface

Start out with a single method isTestChain() that's used by the getblocktemplate RPC.

src/node/interfaces.cpp

@@ -14,6 +14,7 @@
 #include <init.h>
 #include <interfaces/chain.h>
 #include <interfaces/handler.h>
+#include <interfaces/mining.h>
 #include <interfaces/node.h>
 #include <interfaces/wallet.h>
 #include <kernel/chain.h>
@@ -69,6 +70,7 @@ using interfaces::Chain;
 using interfaces::FoundBlock;
 using interfaces::Handler;
 using interfaces::MakeSignalHandler;
+using interfaces::Mining;
 using interfaces::Node;
 using interfaces::WalletLoader;
 using util::Join;
@@ -831,10 +833,26 @@ public:
     ValidationSignals& validation_signals() { return *Assert(m_node.validation_signals); }
     NodeContext& m_node;
 };
+
+class MinerImpl : public Mining
+{
+public:
+    explicit MinerImpl(NodeContext& node) : m_node(node) {}
+
+    bool isTestChain() override
+    {
+        return chainman().GetParams().IsTestChain();
+    }
+
+    NodeContext* context() override { return &m_node; }
+    ChainstateManager& chainman() { return *Assert(m_node.chainman); }
+    NodeContext& m_node;
+};
 } // namespace
 } // namespace node
 
 namespace interfaces {
 std::unique_ptr<Node> MakeNode(node::NodeContext& context) { return std::make_unique<node::NodeImpl>(context); }
 std::unique_ptr<Chain> MakeChain(node::NodeContext& context) { return std::make_unique<node::ChainImpl>(context); }
+std::unique_ptr<Mining> MakeMining(node::NodeContext& context) { return std::make_unique<node::MinerImpl>(context); }
 } // namespace interfaces