Chainparams: Use a regular factory for creating chainparams

src/chainparamsbase.h

@@ -5,6 +5,7 @@
 #ifndef BITCOIN_CHAINPARAMSBASE_H
 #define BITCOIN_CHAINPARAMSBASE_H
 
+#include <memory>
 #include <string>
 #include <vector>
 
@@ -30,6 +31,13 @@ protected:
     std::string strDataDir;
 };
 
+/**
+ * Creates and returns a std::unique_ptr<CBaseChainParams> of the chosen chain.
+ * @returns a CBaseChainParams* of the chosen chain.
+ * @throws a std::runtime_error if the chain is not supported.
+ */
+std::unique_ptr<CBaseChainParams> CreateBaseChainParams(const std::string& chain);
+
 /**
  * Append the help messages for the chainparams options to the
  * parameter string.
@@ -42,8 +50,6 @@ void AppendParamsHelpMessages(std::string& strUsage, bool debugHelp=true);
  */
 const CBaseChainParams& BaseParams();
 
-CBaseChainParams& BaseParams(const std::string& chain);
-
 /** Sets the params returned by Params() to those for the given network. */
 void SelectBaseParams(const std::string& chain);