Don't overwrite custom user defined event id

[Seltsamsel]

In some cases, we already set an event id provided via payloadPairs and it's important for us to keep that event id. However, currently in the core tracker the event id is overwritten no matter what. One very simple solution to this issue is to switch the order of adding the event id and the payloadPairs. In the normal way of using the tracker without providing an own event id, nothing changes.

[Paul Boocock (paulboocock)]

Thanks for the PR @mcepok

We're well on the way to v3 now which sees a significant reshuffle of the codebase. I'm happy to include this change in v3.

If you want to build your own version of sp.js whilst you wait for v3, then you should be able to run: npm run build:all and it'll build core and the tracker then output a new sp.js to /dist.

[Seltsamsel]

We actually want this behavior for the snowplow-nodejs-tracker which, as far as I understood, is based since version 0.4.0 on the core-tracker of this repository. If the next release of the core-tracker is coupled with the javascript-tracker release, that's also fine.

Thanks a lot!

[Paul Boocock (paulboocock)]

I've cherry-picked this into the release/3.0.0 branch and opened corresponding issue #911