[DEV] Implement LinkedInTokenRefresherFunction (timer trigger)

[artcava]

Overview

Implement a new Azure Function LinkedInTokenRefresherFunction with a TimerTrigger that runs on the 1st of every month at 09:00 AM and automatically refreshes the LinkedIn access token via ILinkedInAuthService, writing the new token back to Key Vault.

Depends on: #56 #57

Tasks

• Create src/Functions/LinkedInTokenRefresherFunction.cs:

[Function("LinkedInTokenRefresher")]
public async Task Run(
    [TimerTrigger("%LinkedInTokenRefreshSchedule%")] TimerInfo timer,
    ILogger<LinkedInTokenRefresherFunction> logger)
{
    logger.LogInformation("Starting LinkedIn token refresh...");
    var refreshToken = await _keyVaultService.GetSecretAsync("LinkedInRefreshToken");
    var (newAccessToken, newRefreshToken) = await _linkedInAuthService.RefreshTokenAsync(refreshToken);
    await _keyVaultService.SetSecretAsync("LinkedInAccessToken", newAccessToken);
    if (!string.IsNullOrEmpty(newRefreshToken))
        await _keyVaultService.SetSecretAsync("LinkedInRefreshToken", newRefreshToken);
    logger.LogInformation("LinkedIn token refreshed successfully.");
}

• Add App Setting LinkedInTokenRefreshSchedule = 0 0 9 1 * * (day 1 of every month at 09:00)
• Register dependencies in Program.cs
• Update src/local.settings.json.example with LinkedInTokenRefreshSchedule
• Write unit tests

Acceptance Criteria

• Function triggers correctly on the 1st of the month
• On success: LinkedInAccessToken secret in Key Vault is updated with new value
• On failure: exception is logged with severityLevel >= 3 (triggers alert from [DEV] Implement LinkedInTokenRefresherFunction (timer trigger) #58)
• Idempotent: running twice in a row does not break the token state

Notes

• Schedule 0 0 9 1 * * = every 1st of the month at 09:00 AM — well within the 60-day expiry window
• Use %LinkedInTokenRefreshSchedule% (env var binding) to allow schedule override without redeploy

References

• Analysis document — Section 5, Step 4

[github-actions]

👋 Thanks for opening this issue! A maintainer will review it soon and label it as approved if it can proceed to development.

[artcava]

Deferred

This issue is blocked and deferred until the LinkedIn token refresh strategy is unblocked.

LinkedInTokenRefresherFunction depends on both #56 (IKeyVaultService) and #57 (ILinkedInAuthService), neither of which can be implemented until a valid refresh_token is available. Implementing the timer function without its dependencies would result in dead code.

See #56 for the full reasoning behind this deferral decision. This issue will be re-evaluated alongside #56 and #57 when a viable refresh token strategy is confirmed.