Character limit on identify tracking

[nickjf89]

Describe the bug
I am calling the identify method with a hashed copy of the user's email address. This never appears in the web debugger, but when I change the userId to something short, such as my first name or "test", it works without issue. Is there a character limit applied? The segment debugger doesn't show any signs of errors.

To Reproduce
Steps to reproduce the behavior:

• Do identify(userId: "ee1d83696ded26626ad9fd3f9ad4a28f207cab5a")
• Notice no debugging errors in Xcode, but web debugger doesn't receive event.3.
• Do identify(userId: "test")
• Notice that the event appears in web debugger.
• Expected behavior
• The event should be sent to Segment, and shown in the web debugger.

Platform (please complete the following information):
Library Version in use: 7.9.0
Platform being tested: iOS
Integrations in use: Amplitude

Update
I've since found that there seems to be a character limit applied, as passing ee1d83696ded26626ad9fd3 (a shortened version of the original id) is sent correctly.

Can you advise if this is a bug or expected? For context, we have other teams identifying with strings this length, it only seems to be a problem on the iOS sdk.