jwt flow

[k-capehart]

• [feature]: add auth jwt
• update README
• [fix] auth_test consumerRSAPem
• Update salesforce.go
• fix jwt exp
• small adjustments

Authenticate to Salesforce using the JWT Bearer flow. Docs:

• https://help.salesforce.com/s/articleView?id=sf.remoteaccess_oauth_jwt_flow.htm&type=5
• https://developer.salesforce.com/docs/atlas.en-us.sfdx_dev.meta/sfdx_dev/sfdx_dev_auth_jwt_flow.htm
• https://developer.salesforce.com/docs/atlas.en-us.sfdx_dev.meta/sfdx_dev/sfdx_dev_auth_key_and_cert.htm

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 83.92857% with 9 lines in your changes missing coverage. Please review.

Project coverage is 85.47%. Comparing base (3496b09) to head (5bdcded). Report is 10 commits behind head on main.

Files with missing lines	Patch %	Lines
auth.go	78.57%	5 Missing and 4 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #68 +/- ## ========================================== - Coverage 87.84% 85.47% -2.38% ========================================== Files 6 6 Lines 1111 1404 +293 ========================================== + Hits 976 1200 +224 - Misses 69 134 +65 - Partials 66 70 +4 ```

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[k-capehart]

@TuSKan FYI