m_Payload = Map();
m_Payload.put("client_id","my-unique-client-id");
m_Payload.put("redirect_uri","https://www.joellipman.com");
m_Payload.put("response_type","code");
m_Payload.put("scope","my_api_scopes");
m_Payload.put("prompt","login");

1.  m_Payload = Map(); 
2.  m_Payload.put("client_id","my-unique-client-id"); 
3.  m_Payload.put("redirect_uri","https://www.joellipman.com"); 
4.  m_Payload.put("response_type","code"); 
5.  m_Payload.put("scope","my_api_scopes"); 
6.  m_Payload.put("prompt","login"); 

v_Endpoint = "https://api.joellipman.com/myapi";
l_UrlParams = List();
for each v_Key in m_Payload.keys()
{
	l_UrlParams.add(v_Key.toString() + "=" + m_Payload.get(v_Key));
}
info v_Endpoint + "?" + l_UrlParams.toString("&");

// yields https://api.joellipman.com/myapi?client_id=my-unique-client-id&redirect_uri=https://www.joellipman.com&response_type=code&scope=my_api_scopes&prompt=login

1.  v_Endpoint = "https://api.joellipman.com/myapi"; 
2.  l_UrlParams = List(); 
3.  for each v_Key in m_Payload.keys() 
4.  { 
5.      l_UrlParams.add(v_Key.toString() + "=" + m_Payload.get(v_Key)); 
6.  } 
7.  info v_Endpoint + "?" + l_UrlParams.toString("&"); 
8.   
9.  // yields https://api.joellipman.com/myapi?client_id=my-unique-client-id&redirect_uri=https://www.joellipman.com&response_type=code&scope=my_api_scopes&prompt=login 

v_ReturnedUrl = "https://api.joellipman.com/myapi?isAuthSuccessful=true&code=my_own_code&expires_in=299";
l_ReturnedUrlParts = v_ReturnedUrl.subString(v_ReturnedUrl.indexOf("?")+1).toList("&");
m_UrlParams = Map();
for each  r_Part in l_ReturnedUrlParts
{
	if(r_Part.contains("="))
	{
		l_ParamParts = r_Part.toList("=");
		m_UrlParams.put(l_ParamParts.get(0), l_ParamParts.get(1));
	}
}

1.  v_ReturnedUrl = "https://api.joellipman.com/myapi?isAuthSuccessful=true&code=my_own_code&expires_in=299"; 
2.  l_ReturnedUrlParts = v_ReturnedUrl.subString(v_ReturnedUrl.indexOf("?")+1).toList("&"); 
3.  m_UrlParams = Map(); 
4.  for each  r_Part in l_ReturnedUrlParts 
5.  { 
6.      if(r_Part.contains("=")) 
7.      { 
8.          l_ParamParts = r_Part.toList("="); 
9.          m_UrlParams.put(l_ParamParts.get(0), l_ParamParts.get(1)); 
10.      } 
11.  }