[#F28B9F260B53F7C9A88D955BF9053CCDE8701D3C]
Replace params
iterator replace( iterator pos, param_pct_view const& p);
This function replaces the contents of the element at `pos` with the specified param.
All iterators that are equal to `pos` or come after are invalidated.
The strings passed in must not come from the element being replaced, or else the behavior is undefined.
url u( "?first=John&last=Doe" );
u.encoded_params().replace( u.encoded_params().begin(), { "title", "Mr" });
assert( u.encoded_query() == "title=Mr&last=Doe" );
Linear in `this->url().encoded_query().size()`.
Strong guarantee. Calls to allocate may throw. Exceptions thrown on invalid input.