Get a log upload URL

Called by the MineOS device agent to upload its diagnostic log after a scan; you do not call this endpoint yourself.
The agent authenticates with its device certificate, declares the log id and compressed size, and receives a short-lived
URL to upload the log to. MineOS stores the log for support purposes only.

Responses:

• 200 — { "uploadUrl", "expiresAt", "requiredContentType" }: upload the log with an HTTP PUT to uploadUrl
  before expiresAt
• 400 — { "error": "invalid_request", "details": [ ... ] }: the request is malformed or contains unknown fields
• 403 — { "reason": "enrollment_not_active" }: the device is not (or no longer) an approved device
• 413 — { "reason": "log_too_large" }: the declared size is over the limit
• 429 — { "reason": "quota_exceeded" | "rate_limited", "retryAfter" }: the device's daily log quota or your
  organization's rate limit is reached
• 503 — { "status": "degraded" }: log storage is temporarily unavailable; the agent retries