1. A method, comprising: receiving, by a computing system, requests to establish transaction accounts at a computing system, wherein the requests are associated with respective different partner entities of a plurality of partner entities, wherein the requests have different formats, wherein a first request is received via a web service provided by a partner application server that communicates the first request to the computing system using a predefined application programming interface (API), and wherein a second request is received based on user access to a microsite provided by the computing system in response to a partner web server redirecting a user to an address of the computing system and indicating a return address of the partner web server, wherein the microsite is formatted to match a site of a corresponding partner entity; storing, by the computing system, web content for respective ones of the plurality of partner entities; receiving, for each of the first and second requests, an identifier of the partner entity associated with the respective request; invoking, by the computing system in response to each of the first and second requests, a same particular code block to perform an action for the respective request, wherein the action includes retrieving and providing web content to be displayed to a customer of the respective partner entity associated with the request based on the identifier of the respective partner entity, wherein the web content identifies the respective partner entity and is formatted and branded to maintain the look and feel of a website of the partner entity; and generating and transmitting authorization responses for the first and second requests, wherein at least one of the authorization responses authorizes establishment of a transaction account and includes account information for the authorized transaction account.