feat!: Use strings from spec for error and reason enums

[alxckn]

Fixes #123

Upper cases error and reason enum values and adds missing 'PROVIDER_FATAL' error

[codecov[bot]]

Codecov Report

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

Project coverage is 99.48%. Comparing base (33843f9) to head (3353179).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #131 +/- ## ======================================= Coverage 99.48% 99.48% ======================================= Files 15 15 Lines 195 196 +1 ======================================= + Hits 194 195 +1 Misses 1 1 ```

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