[CONFIG] Migrate LinkedIn credentials to Key Vault References

[artcava]

Overview

Replace the static LINKEDIN_ACCESS_TOKEN, LINKEDIN_CLIENT_ID, and LINKEDIN_CLIENT_SECRET App Settings with Azure Key Vault References, so the Function App always reads the latest secret version without restarts.

Depends on: #54

Tasks

• Update the following Azure App Settings to Key Vault References:
  • LINKEDIN_ACCESS_TOKEN → @Microsoft.KeyVault(VaultName=xposter-kv;SecretName=LinkedInAccessToken)
  • LINKEDIN_CLIENT_ID → @Microsoft.KeyVault(VaultName=xposter-kv;SecretName=LinkedInClientId)
  • LINKEDIN_CLIENT_SECRET → @Microsoft.KeyVault(VaultName=xposter-kv;SecretName=LinkedInClientSecret)
• Add KEYVAULT_URI App Setting: https://xposter-kv.vault.azure.net/
• Verify InSender still works correctly after migration (no code change expected)
• Update src/local.settings.json.example with new variable structure and Key Vault reference format
• Update docs/configuration.md documenting Key Vault reference syntax

Acceptance Criteria

• LinkedIn posts publish successfully after the migration
• Azure Portal shows Key Vault Reference status as ✅ (green) for all three settings
• No plain-text secrets visible in Application Settings

Notes

• Use unversioned Key Vault References (without SecretVersion) so the app always resolves the latest version automatically after each token refresh
• InSender requires zero code changes — the runtime resolves the reference transparently

References

• Analysis document — Section 5, Step 3

[github-actions]

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