fix: allow users to pass `nkeys_seed_str` as argument for NATS broker.

[Drakorgaur]

This would simplify the usage of applications without a need to read files.

Description

Please include a summary of the change and specify which issue is being addressed. Additionally, provide relevant motivation and context.

Fixes # (issue number)

Type of change

Please delete options that are not relevant.

• [ ] Documentation (typos, code examples, or any documentation updates)
• [ ] Bug fix (a non-breaking change that resolves an issue)
• [x] New feature (a non-breaking change that adds functionality)
• [ ] Breaking change (a fix or feature that would disrupt existing functionality)
• [ ] This change requires a documentation update

Checklist

• [x] My code adheres to the style guidelines of this project (scripts/lint.sh shows no errors)
• [x] I have conducted a self-review of my own code
• [x] I have made the necessary changes to the documentation
• [x] My changes do not generate any new warnings
• [ ] I have added tests to validate the effectiveness of my fix or the functionality of my new feature
• [ ] Both new and existing unit tests pass successfully on my local environment by running scripts/test-cov.sh
• [ ] I have ensured that static analysis tests are passing by running scripts/static-analysis.sh
• [ ] I have included code examples to illustrate the modifications

[Lancetnik]

Thank you a lot for the PR! Can it wait a few days? I didn't want to release a new version so far

[Drakorgaur]

Thank you a lot for the PR! Can it wait a few days? I didn't want to release a new version so far

Of course! Thanks for fast check, review and feedback :)