Any news about this issue? We have the same requirement, we need to pass custom headers required by our reverse proxy. I saw that this will be possible with the new Quartz SDK (AGSRequestConfiguration::useHeaders : https://developers.arcgis.com/ios/beta/api-reference//interface_a_g_s_request_configuration.html#a47fd4ec9f76579aeab5b7c74a6f68fe6) so I guess we have to wait for it.
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