1. A system for providing endpoint management of application programming interfaces, the system comprising: an electronic data store configured to store application programming interface (“API”) mapping definitions; and an endpoint system comprising one or more hardware computing devices executing specific computer-executable instructions, wherein the endpoint system is in communication with the electronic data store, and configured to at least: receive a plurality of API mapping definitions, wherein each respective API mapping definition associates a proxy API with at least one endpoint API; receive a request from a calling system to execute a program code by a particular proxy API; determine, based at least in part on the received request and the particular proxy API, an API mapping definition associated with the particular proxy API; transform the request into an endpoint request for processing by an endpoint API system, wherein the request is transformed based at least in part on the API mapping definition and wherein the endpoint request includes an instruction to execute the program code on the endpoint API system; transmit the endpoint request to the endpoint API system to cause execution of the program code on the endpoint API system; receive an endpoint result from the endpoint API system, wherein the endpoint result is generated from the execution of the program code on the endpoint API system; transform the endpoint result into a proxy result, wherein the endpoint result is transformed based at least in part on the API mapping definition; and provide a return response to the calling system, wherein the return response comprises at least the proxy result.