Update all Elixir Exercism repos to use Elixir 1.15 and OTP 26

[angelikatyborska]

An example of how to do it can be seen in previous PRs for Elixir 1.14:

• https://github.com/exercism/elixir/pull/1191 (note that the oldest Elixir version gets dropped)
• https://github.com/exercism/elixir-test-runner/pull/92
• https://github.com/exercism/elixir-analyzer/pull/325
• https://github.com/exercism/elixir-representer/pull/72

[dabaer]

@angelikatyborska I was just peeking into this when I noticed you assigned this ha!

At first glance some minor changes to mix.exs and an upgrade to dialyxer.

I'm running into an issue with the TakeANumberDeluxe test (🤔 didn't we just fix an issue on that one?) where the GenServer is exiting on invalid configuration. Just going over that at the moment

[angelikatyborska]

Ah, sorry 😅 I opened a draft PR https://github.com/exercism/elixir/pull/1332 - draft because I don't know yet how to handle that failing TakeANumberDeluxe test. Let me know if you figure it out!

[dabaer]

All good! I'll dig it out and then move over to your PR discussion

[angelikatyborska]

@dabaer If you're interested in helping out further, now that https://github.com/exercism/elixir/pull/1332 is merged, you could open PRs for the 3 other repositories

[dabaer]

Will do 🎉

[dabaer]

♥️💙💚💛💜

[angelikatyborska]

It's live and I wrote a little site update:

[dabaer]

It was a wild ride with breaking changes, and certainly one of the largest PR threads I've ever seen.

Thank you and @neenjaw for your guidance on these commits, it's really expanded my knowledge of Elixir!