Enforce Trailing Slash On Go RPC URLs

[THEjacob1000]

Internal change only

This pull request improves the handling of base URLs in the lokerpc client by ensuring they are consistently normalized. It introduces a utility function to standardize base URLs and adds comprehensive tests to verify this behavior.

Submitter Checklist

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• Self-reviewed code, removed extraneous comments, debug logging, checked code style
• No change to users after merge (off-by-default configuration, feature flag, alt URL, etc.) and can be disabled if issues arise (if this is not the case we may need stakeholder signoff)
• Changes are documented (README, wiki, etc)
• Automated tests added or existing tests cover the new functionality or changes
• Manually tested changes
• Metrics added to track the usage/performance
• I am confident I can revert this change
• Database migrations are reversible without data loss (if applicable)
• Performance impact is acceptable (if applicable)
• Any new dependencies are justified or have been approved (if applicable)
• This is NOT a high risk change (if it is, please follow the high-risk change process)

Testing Evidence

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• Test cases cover the new functionality or changes
• Screenshots or logs of the changes (if applicable)
• Performance benchmarks (if applicable)
• Storybook cases (if applicable)

Reviewer Checklist

Note: if this PR affects authentication or payments please seek a secondary tester.

• I am ok with code style and functionality
• I have personally tested the feature
• My review was not rushed due to time constraints

[THEjacob1000]

mimicked functionality from @loke/http-rpc-client: https://github.com/LOKE/loke-http-rpc-client/blob/master/src/client.ts#L17-L19

[smithamax]

Not that it really matters, but it probably shouldn't strip multiple /