Include Customer ID in Memberships Export

🔍 Problem Statement
As a data analyst, I experience the memberships export having no way to link a membership to a customer when the email field is blank, which breaks data analysis and cross-system matching.

💡 User Story
As a data analyst, I want the memberships export to include the Pelcro customer ID, so that I can reliably join membership data with customer records even when email is absent.

🎯 Definition of Done
- Given the memberships export, when downloaded, then a customerId column is included in every row.
- This change impacts the API (memberships export endpoint).
- Limitations: customer ID is the Pelcro internal ID; no additional PII is added beyond what is already exported.

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What would you like to be able to do? (One idea per form): Include customer id in the memberships export. How would that help you?: Currently the memberships export provides no way to relate a membership with a customer when the email address is blank. That would be useful for data analysis. How important is this to you?: Important Email address: mgilbert@crain.com ——————————————— This task was submitted through Suggest an idea https://form.asana.com/?k=qsv6hMm2wL8SXD_R-h-N9Q&d=742417627358732