Add v1.x deprecation warning

[mfisher87]

Closes #545

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Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 65.20%. Comparing base (bea9fe0) to head (c6811c7). Report is 1 commits behind head on development.

:exclamation: There is a different number of reports uploaded between BASE (bea9fe0) and HEAD (c6811c7). Click for more details.

HEAD has 1 upload less than BASE

| Flag | BASE (bea9fe0) | HEAD (c6811c7) | |------|------|------| ||3|2|

Additional details and impacted files

```diff @@ Coverage Diff @@ ## development #603 +/- ## =============================================== - Coverage 71.57% 65.20% -6.37% =============================================== Files 37 37 Lines 3061 3064 +3 Branches 596 596 =============================================== - Hits 2191 1998 -193 - Misses 766 981 +215 + Partials 104 85 -19 ```

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[mfisher87]

I really wish I had more time to get the integration test workflow all smoothed out. Not sure what's going on :(