Adds OPERA-S1 PRODUCT_TYPE constants

[codecov-commenter]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (a2fc3c4) 89.85% compared to head (baeaa3c) 89.87%. Report is 7 commits behind head on master.

Files	Patch %	Lines
asf_search/ASFSearchOptions/validators.py	73.91%	6 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #250 +/- ## ========================================== + Coverage 89.85% 89.87% +0.02% ========================================== Files 54 54 Lines 2021 2025 +4 ========================================== + Hits 1816 1820 +4 Misses 205 205 ``` | [Flag](https://app.codecov.io/gh/asfadmin/Discovery-asf_search/pull/250/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=asfadmin) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/asfadmin/Discovery-asf_search/pull/250/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=asfadmin) | `89.87% <77.77%> (+0.02%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=asfadmin#carryforward-flags-in-the-pull-request-comment) to find out more.

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