refactor: rpc: set TxToJSON default verbosity to SHOW_DETAILS

`TxToJSON()` and `TxToUniv()` are only to be called when we want to
decode the transaction (i.e. its details) into JSON. If `TxVerbosity` is
`SHOW_TXID`, the function should not have been (and currently is not)
called in the first place.

There is no behaviour change, current logic simply assumes anything less
than `TxVerbosity::SHOW_DETAILS_AND_PREVOUT` equals
`TxVerbosity::SHOW_DETAILS`. With this change, the assumptions and
intent become more explicit.

Author: stickies-v

src/core_write.cpp

@@ -170,6 +170,8 @@ void ScriptToUniv(const CScript& script, UniValue& out, bool include_hex, bool i
 
 void TxToUniv(const CTransaction& tx, const uint256& block_hash, UniValue& entry, bool include_hex, int serialize_flags, const CTxUndo* txundo, TxVerbosity verbosity)
 {
+    CHECK_NONFATAL(verbosity >= TxVerbosity::SHOW_DETAILS);
+
     entry.pushKV("txid", tx.GetHash().GetHex());
     entry.pushKV("hash", tx.GetWitnessHash().GetHex());
     // Transaction version is actually unsigned in consensus checks, just signed in memory,

src/rpc/rawtransaction.cpp

@@ -54,8 +54,11 @@ using node::PSBTAnalysis;
 using node::ReadBlockFromDisk;
 using node::UndoReadFromDisk;
 
-static void TxToJSON(const CTransaction& tx, const uint256 hashBlock, UniValue& entry, Chainstate& active_chainstate, const CTxUndo* txundo = nullptr, TxVerbosity verbosity = TxVerbosity::SHOW_TXID)
+static void TxToJSON(const CTransaction& tx, const uint256 hashBlock, UniValue& entry,
+                     Chainstate& active_chainstate, const CTxUndo* txundo = nullptr,
+                     TxVerbosity verbosity = TxVerbosity::SHOW_DETAILS)
 {
+    CHECK_NONFATAL(verbosity >= TxVerbosity::SHOW_DETAILS);
     // Call into TxToUniv() in bitcoin-common to decode the transaction hex.
     //
     // Blockchain contextual information (confirmations and blocktime) is not