Add --server flag to override server given to ferry-cli

[shreyb]

Closes #99

Adds a new flag, -s/--server, that allows for users to override the configured api.base_url value. This allows for quick testing of different FERRY instances.

Also added unit tests for both the changed functionality in the FerryCLI class, and the overall CLI and new flag.

All unit tests pass, as well as the following check:

$ ./bin/ferry-cli --dryrun --server https://fakeserver:12345  -e ping

Would call endpoint: https://fakeserver:12345/ping with params
{}

[Copilot]

Pull Request Overview

This PR adds a new command-line flag -s/--server that allows users to override the configured api.base_url value for quick testing of different FERRY instances.

• Adds server flag to auth parser with help text
• Modifies FerryCLI constructor to accept optional base_url parameter
• Updates main function to pass server flag value to FerryCLI constructor
• Adds comprehensive unit tests for both FerryCLI class and CLI functionality
• Refactors existing test to use parametrized approach

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated no comments.

File	Description
ferry_cli/helpers/auth.py	Adds the new -s/--server argument to the auth parser
ferry_cli/main.py	Updates FerryCLI constructor to accept base_url parameter and modifies main function to pass server flag
tests/test_main.py	Adds unit tests for server flag functionality and refactors existing test to use pytest parametrize

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