start to implement session::find()

include/matador/sql/session.hpp

@@ -39,7 +39,12 @@ public:
     }
     // collect all columns
     // - evaluate fetch::Eager flag for relations
+    auto info = schema_->info<Type>();
+    if (!info) {
+      return {};
+    }
 
+    c->query(*schema_).select({}).from(info->name);
     // build pk where condition
     // - check if type has pk
     // - check type