Add first round of kuzu -> nim type conversions.

FossilOrigin-Name: 7435f8dcdff8f0a22eb1a07b4e19f379dd731e6557eeefb5dbf75f5b32cb82ed

tests/values/t_raise_error_on_invalid_conversion.nim

@@ -0,0 +1,24 @@
+# vim: set et sta sw=4 ts=4 :
+
+import
+  std/re
+import kuzu
+
+let db = newKuzuDatabase()
+let conn = db.connect
+
+var q = conn.query( "CREATE NODE TABLE Doop ( id SERIAL, thing STRING, PRIMARY KEY(id) )" )
+
+q = conn.query( "CREATE (d:Doop {thing: 'okay!'})" )
+q = conn.query( "MATCH (d:Doop) RETURN d" )
+
+var tup = q.getNext
+var val = tup[0]
+assert val.kind == KUZU_NODE
+
+try:
+    discard val.toInt32
+except KuzuTypeError as err:
+    assert err.msg.contains( re"""Mismatched types: KUZU_NODE != int32""" )
+
+