Missing Channel ID could be clearer

### Environment SaaS ([https://sentry.io/](<https://sentry.io/>)) ### Steps to Reproduce 1. Create a new metric alert, or edit an existing one 2. Add an action with Discord as the target 3. Leave the channel ID blank 4. Save Rule ### Expected Result The empty field should be highlighted, or the error should state which specific field is missing. Or do both. ### Actual Result When saving a metric alert with a discord action and no channel ID, the error thrown is not clear which field is missing  ### Product Area Alerts ### Link *No response* ### DSN *No response* ### Version *No response* We want to define a set of [lightweight metrics](<https://docs.sentry.io/product/explore/metrics/>) that SDKs can automatically collect for e.g. framework, language or platform, focusing only on signals that **do NOT overlap with Tracing**. Ideally these metrics should give a quick sense of app or runtime health, … while deeper investigation will still rely on traces or profiles.<br><br>Examples**:** * Node.js runtime metrics (e.g., event loop delay, heap usage) * Prisma-related metrics in Next.js * Mobile CPU / memory usage to help surface potential ANRs or app hangs --- **Candidate Metrics (add more below)** * … *(please also add ideas, questions or examples in comments)*