Add support for multiple headers with same key

[k4i6]

Closes #776

• Add support for multiple header entries with same name for api responses in the backend

Backwards compatibility

• The interface Map<String, String> is still supported, but marked as deprecated

Additional Notes

• The client api is unchanged: Since the fetch api doesn't allow multiple header entries with the same key, the current implementation seems sufficient to me

[bitspittle]

Thanks for the PR. I will be busy for a few more days, so apologies for the delay in advance.

I'll add reminders to take a look at this by the end of this week, but if you don't hear from me by the weekend, you can definitely reach out!

[k4i6]

@bitspittle friendly reminder: Did you already have a chance to look into this?

[bitspittle]

Major apologies! I did not forget. And I should have given you an update. I hate sounding like I'm making excuses, but last week was crazy and this week will likely be too. I do have a daily reminder to review this PR so I promise it won't get dropped.

You are free to skip the rest of this reply! But I'll explain here what's been going on to give you an idea if you're curious. I also want to emphasize that this stuff is temporary chaos that should be settling down soon.

We're fostering three dogs here -- and last Tuesday we had a parasite scare, so we've been managing that with meds while also cleaning all sheets and dog beds and surfaces in our house to reduce the chance it will happen again. One of the three also got neutered last week in the middle of all this, something else we've had to manage. He already wants to play with everyone else, and we can't let him, which is... fun. It requires full time management basically.

At the same time, we also got a ton of interest for all three dogs which means a lot of calling and vetting people, which will continue through the next few days. Finally, my wife has a minor surgical procedure Thursday this week, so we're juggling prep for that right now.

By next week, we expect two if not all three dogs to be adopted and the wife to be back in commission, at which point I plan to block off time to really focus on all my coding tasks that have fallen behind on.

I still need to get on top of some of my lingering Kotter work, because otherwise I'll be too scatter-brained to give your PR the attention it needs, because I assume this area will need a bit of thought regarding backwards compatability.

If I end up getting more time than I expect, I will look at this early. But we're looking at midweek next week at this point. My apologies for that.

[k4i6]

Thanks for the update, no worries at all — I completely understand, and it sounds like you’ve had your hands full! Wishing your wife a smooth procedure and recovery, and I hope things settle down soon with the dogs too.

[bitspittle]

Well, good news and bad news!

The good news is the medical procedure went very well and results were best case scenario.

Bad news is, and this was our first experience with this, but the adopter who took one of our dogs turned out to have lied to us about almost everything, and we spent the weekend getting her back after realizing it.

Of the three dogs, this one is a border collie, which among our fosters accounted for about 90% of our time and energy.... So we're back to the adoption drawing board with her, and this will definitely affect the free time I was planning on having this week.

I'll make progress on my projects as I get time to do so. Hopefully I'll still be getting to this review in the not-so-distant future. But I wanted to give you heads up that things are in a bit of a continued disarray here for now :)