Add example for alerts in YAML (#135)

Author: shreyas-goenka

knowledge_base/alerts/README.md

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+# SQL Alerts with Databricks Asset Bundles
+
+This example shows how to define SQL alerts using Databricks Asset Bundles. The alert monitors daily NYC Taxi revenue and triggers when it exceeds a threshold.
+
+For more information about SQL alerts, see the [Databricks documentation](https://docs.databricks.com/aws/en/sql/user/alerts/).
+
+## Usage
+
+1. Modify `databricks.yml`:
+   - Update the `host` field to your Databricks workspace URL
+   - Update the `warehouse` field to the name of your SQL warehouse
+
+2. Modify `resources/nyc_taxi_daily_revenue.alert.yml`:
+   - Update the `user_name` field under `permissions` to your email address
+
+3. Deploy the alert:
+   ```sh
+   databricks bundle deploy
+   ```
+
+## Key Configuration
+
+The alert configuration in `resources/nyc_taxi_daily_revenue.alert.yml` includes:
+
+- **query_text**: SQL query that returns the metric to monitor
+- **evaluation**: Defines how to evaluate the query results
+  - `comparison_operator`: GREATER_THAN, LESS_THAN, EQUAL, etc.
+  - `source.aggregation`: MAX, MIN, AVG, or SUM
+  - `threshold.value`: The value to compare against
+- **schedule**: Uses Quartz cron syntax (e.g., `"0 0 8 * * ?"` for daily at 8 AM)
+- **warehouse_id**: The SQL warehouse to execute the query

knowledge_base/alerts/databricks.yml

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+bundle:
+  name: alerts
+
+include:
+  - resources/*.yml
+
+variables:
+  # The "warehouse_id" variable is used to reference the warehouse used by the alert.
+  warehouse_id:
+    lookup:
+      # Replace this with the name of your SQL warehouse.
+      warehouse: "Shared Unity Catalog Severless"
+
+workspace:
+  host: https://myworkspace.databricks.com
+
+
+targets:
+  dev:
+    default: true
+    mode: development

knowledge_base/alerts/resources/nyc_taxi_daily_revenue.alert.yml

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+resources:
+  alerts:
+    nyc_taxi_daily_revenue:
+      permissions:
+        - level: CAN_MANAGE
+          user_name: user@company.com
+
+      custom_summary: "Alert when NYC Taxi daily revenue exceeds threshold"
+      display_name: "NYC Taxi Daily Revenue Alert"
+
+      # The SQL query that the alert will evaluate
+      query_text: |
+        SELECT
+          to_date(tpep_pickup_datetime) as date,
+          SUM(fare_amount) as amount
+        FROM
+          `samples`.`nyctaxi`.`trips`
+        GROUP BY
+          ALL
+        ORDER BY
+          1 DESC
+
+      # The warehouse to use for running the query
+      warehouse_id: ${var.warehouse_id}
+
+      evaluation:
+        # Comparison operator for the threshold
+        comparison_operator: "GREATER_THAN"
+
+        # Notification settings
+        notification:
+          notify_on_ok: false
+          retrigger_seconds: 3600  # Re-trigger after 1 hour if condition persists
+
+        # Source defines which column and aggregation to evaluate
+        source:
+          aggregation: "MAX"
+          display: "amount"
+          name: "amount"
+
+        # Threshold to compare against
+        threshold:
+          value:
+            double_value: 1000000.0  # Alert if daily revenue exceeds $1M
+
+      # Schedule for running the alert
+      schedule:
+        pause_status: "UNPAUSED"
+        quartz_cron_schedule: "0 0 8 * * ?"  # Run daily at 8 AM UTC
+        timezone_id: "UTC"