Finds a program membership by external_user_id.
the external user id to update the program membership with
GET /partner-api/v2/program-memberships/search HTTP/1.1 Host: X-API-Key: YOUR_API_KEY Accept: */*
Membership was found with provided wallet_address, on_chain_token_id, and/or external_user_id
{ "membership": { "id": "text", "external_user_id": "text", "wallet_address": "text", "profile_image": "text", "on_chain_token_id": "text", "created_at": 1, "social_media_credentials": { "twitter_username": "text", "instagram_username": "text", "tiktok_username": "text" }, "family_member_birthdays": [ "text" ] } }