PrebidMobile.setExternalUserIds is not adding external users

[kwchan22]

Describe the bug
PrebidMobile.setExternalUserIds(...) does not set the userIds in the Prebid bid request user section. However if using TargetingParams.storeExternalUserId then I see the userId in the bid request.

To Reproduce
Steps to reproduce the behavior:

1. Git clone Prebid Android SDK Project
2. Go to PrebidDemoKotlin -> CustomApplication.kt
3. Add in onCreate() this code: PrebidMobile.setExternalUserIds(mutableListOf(ExternalUserId("PrebidMobile", "prebidMobile-123", null, null)))
4. Run app with App inspection
5. See under the network inspector -> "/auctions" endpoint, I do not see the user added.

Expected behavior
All the users set with PrebidMobile.setExternalUserIds should be added to the Prebid bid request user section.

Screenshots
With PrebidMobile.setExternalUserIds, bid request user is empty

With TargetingParams.storeExternalUserId, user has the externalUserId

Desktop (please complete the following information):
MacBook Pro Apple M3 Pro

Smartphone (please complete the following information):

• Device: Google Pixel 4
• OS: Android 11

Additional context
None

[sarbyn]

Same here on android with prebid version 2.2.3
This happens also with prebid 2.1.1

[YuriyVelichkoPI]

@OlenaPostindustria, please check the behaviour on iOS.

[OlenaPostindustria]

Hi, on iOS both methods for setting external users - using Targeting or Prebid - work properly. However, when both methods are applied, the data set through Targeting takes priority over the data set via Prebid.

Ref: https://github.com/prebid/prebid-mobile-ios/blob/46e330f6a683f2086914a861af4b9fbfefd8e33d/PrebidMobile/ConfigurationAndTargeting/Targeting.swift#L239

[YuriyVelichkoPI]

Hi @sarbyn! I'd like to propose the following fix:

1. Deprecate PrebidMobile.setExternalUserIds
2. Introduce TargetingParams.setExternalUserIds that will accept the array of IDs.

The motivation for this is as follows:

• The class PrebidMobile should be used to tune the SDK behavior, such as request timeout.
• The class TargetingParams should be used to modify the bid request.

[ValentinPostindustria]

Hello.
We compared implementation with OpenRTB standard. During testing, we found some problems and limitations of ExternalUserId.

1. The SDK sends adtype instead of atype.

                {
                    "source": "sharedid.org",
                    "uids": [
                        {
                            "adtype": 1,
                            "ext": {
                                "third": "01ERJWE5FS4RAZKG6SKQ3ZYSKV"
                            },
                            "id": "111111111111"
                        }
                    ]
                }

2. It's impossible to set many uids objects for one source in the code. But according to the documentation it is acceptable.

          "uids": [
            {
              "id": "yyy",
              "atype": 1
            },
            {
              "id": "zzz",
              "atype": 1
            },
            {
              "id": "DB700403-9A24-4A4B-A8D5-8A0B4BE777D2",
              "atype": 2
            }
          ]

3. Currently the SDK stores Extended Identifiers in the permanent storage, so they will be restored after restarting the app. Do we need to store them like this?