I found this snippet in the FAQ on the GNU website
https://www.gnu.org/licenses/gpl-faq.html#AGPLv3ServerAsUser
If some network client software is released under AGPLv3, does it have to be able to provide source to the servers it interacts with? (#AGPLv3ServerAsUser)
AGPLv3 requires a program to offer source code to “all users interacting with it remotely through a computer network.” It doesn’t matter if you call the program a “client” or a “server,” the question you need to ask is whether or not there is a reasonable expectation that a person will be interacting with the program remotely over a network.For software that runs a proxy server licensed under the AGPL, how can I provide an offer of source to users interacting with that code? (#AGPLProxy)
For software on a proxy server, you can provide an offer of source through a normal method of delivering messages to users of that kind of proxy. For example, a Web proxy could use a landing page. When users initially start using the proxy, you can direct them to a page with the offer of source along with any other information you choose to provide.The AGPL says you must make the offer to “all users.” If you know that a certain user has already been shown the offer, for the current version of the software, you don’t have to repeat it to that user again.