Add basic auth deprecation warnings for May 3rd retirement

[samsolaimani]

Summary

• Displays a yellow bordered warning banner every time a command runs using basic auth (password), directing users to migrate to OAuth2
• Adds the same deprecation warning at the start of alks developer login
• Updates the password choice label in alks developer configure to reflect the May 3rd retirement date
• Adds a "did you mean?" tip when a user has configured https://alks.coxautoinc.com without the required /rest path

Test plan

Basic auth deprecation warning

• Run any alks command (e.g. sessions open) configured with basic auth — confirm the yellow deprecation warning banner appears in the terminal
• Run alks developer login — confirm warning appears before credential prompts
• Run alks developer configure — confirm password choice shows "(DEPRECATED - retiring May 3rd, not recommended)"
• Run any command configured with OAuth2 (refresh token) — confirm no warning appears

"Did you mean?" server URL hint

• Set ALKS_SERVER=https://alks.coxautoinc.com and run alks sessions open — confirm the yellow tip appears: "Did you mean https://alks.coxautoinc.com/rest?"
• Set ALKS_SERVER=https://alks.coxautoinc.com/ (trailing slash) and run alks sessions open — confirm tip still appears
• Set ALKS_SERVER=https://alks.coxautoinc.com/rest and run alks sessions open — confirm no tip appears
• Set a completely different server URL — confirm no tip appears

Rally

US1879500: Create warning for ALKS CLI basic auth deprecation

[DevOpsDave]

@samsolaimani looking at this now

[DevOpsDave]

Bug: Deprecation warning shows 3 times per command

When running alks session open with password auth, the bordered deprecation warning appears 3 times because getAuth() is called multiple times during a single command invocation:

1. ensureConfigured() → getAuthButDontThrow() → getAuth()
2. getIamKey() → getAuth()
3. promptForAlksAccountAndRole() → getAlksAccounts() → getAuth()

Each call hits the password path and triggers showBorderedMessage.

Suggested fix: Add a module-level flag in getAuth.ts to only show the warning once per process:

let deprecationWarningShown = false;

// ... inside the password branch:
if (!deprecationWarningShown) {
  showBorderedMessage(
    80,
    yellow(
      '⚠  DEPRECATION WARNING: Basic Authentication (network password) will be\n' +
        '   retired on May 3rd. Please run `alks developer configure` to migrate\n' +
        '   to OAuth2 (refresh token) authentication.'
    )
  );
  deprecationWarningShown = true;
}

Reproduced with: node dist/src/bin/alks.js session open -a awsmarvenintnp -r Admin -o env -N -D 1

[DevOpsDave]

@samsolaimani Do we want to show the Deprecation warnings 3 times?

One time when we pick basic auth and then one time when we make a session I think is good. In the PR I have a suggestion on how to fix.

[DevOpsDave]

@samsolaimani see my comments.