fix(cache): Nil panic from elasticcache new endpoint

[dee0]

Description of your changes

Add a test case that replicates issue #1838 and a fix for same.
NOTE:
Test case is a little different from others because I wanted the mock to replicate as closely as possible the we saw from AWS when we encountered #1838. That is, I didn't want to fix the panic we saw only to find out there were other problems we weren't aware of. Anyhoo, this meant setting some fields in the mock that no other Observe tests are setting.

Fixes #1838

I have:

• Read and followed Crossplane's [contribution process].
• Run make reviewable test to ensure this PR is ready for review.

How has this code been tested

I added a test case that reproduces the issue to the Observe test.
I made my change and confirmed that my new test case passed.
I then confirmed that all existing cache tests still passed.

[MisterMX]

LGTM. Thank you very much @dee0. Can you solve the conflicts and squash your changes into a single commit?

[dee0]

Hey @MisterMX
Thanks for looking at this.

Squashed my commits and merged the latest master into my branch to resolve the merge conflict.

While the merge conflicts are one and there is just 1 commit from me showing, the PR is saying there are 11 commits total. Think Github may be confused. :)

In any case, please let me know if there is something more for me to do.

[MisterMX]

@dee0 thanks for doing the fix. It is generally not recommended to use git merge to update a feature branch with master because it will create a merge commit that is probably confusing Git. It is better to use git rebase in such case.

To provide a clean history (only a single commit) can you do a clean rebase so you only have a single commit left? You can drop the other commits in an interactive rebase using git rebase -i. If that, for any reason, doesn't work you can delete the branch locally, create it anew, cherry pick the changes you need and push it again.

I hope that isn't too inconvenient to you, but I would like to keep the upstream repo as clean as possible.

[dee0sap]

Hey @MisterMX

No worries I'll try to sort out.

[dee0sap]

Hey @MisterMX
Now down to 1 commit.

[MisterMX]

LGTM. Thank you very much @dee0!