(docs): add custom dashboard in app documentation

close #6982

ui/src/assets/markdown/dashboard_home.md

@@ -1,3 +1,127 @@
 # Custom Dashboard Feature
 
 Welcome to the Custom Dashboard! This feature allows you to create and manage personalized dashboards to monitor and visualize your data effectively.
+
+## Create a new Dashboard as code
+
+Below is an example of a dashboard definition that displays executions over time and a pie chart of execution states:
+
+```yaml
+title: Getting Started
+description: First custom dashboard
+timeWindow:
+  default: P7D
+  max: P365D
+charts:
+  - id: executions_timeseries
+    type: io.kestra.plugin.core.dashboard.chart.TimeSeries
+    chartOptions:
+      displayName: Executions
+      description: Executions last week
+      legend:
+        enabled: true
+      column: date
+      colorByColumn: state
+    data:
+      type: io.kestra.plugin.core.dashboard.data.Executions
+      columns:
+        date:
+          field: START_DATE
+          displayName: Date
+        state:
+          field: STATE
+        total:
+          displayName: Executions
+          agg: COUNT
+          graphStyle: BARS
+        duration:
+          displayName: Duration
+          field: DURATION
+          agg: SUM
+          graphStyle: LINES
+
+  - id: executions_pie
+    type: io.kestra.plugin.core.dashboard.chart.Pie
+    chartOptions:
+      graphStyle: DONUT
+      displayName: Total Executions
+      description: Total executions per state
+      legend:
+        enabled: true
+      colorByColumn: state
+    data:
+      type: io.kestra.plugin.core.dashboard.data.Executions
+      columns:
+        state:
+          field: STATE
+        total:
+          agg: COUNT
+```
+
+To see all available properties to configure a custom dashboard as code, see examples provided in the [Enterprise Edition Examples](https://github.com/kestra-io/enterprise-edition-examples) repository.
+
+## Querying data
+
+The `data` property of a chart defines the type of data that is queried and displayed. The `type` determines which columns are displayed.
+
+Dashboards can query data from these source `types`:
+- `type: io.kestra.plugin.core.dashboard.data.Executions`: data related to your workflow executions
+- `type: io.kestra.plugin.core.dashboard.data.Logs`: logs produced by your workflows
+- `type: io.kestra.plugin.core.dashboard.data.Metrics`: metrics emitted by your plugins
+
+After defining the data source, specify the columns to display in the chart. Each column is defined by the `field` and may include additional optional properties.
+
+
+| Property | Description                                                                                                    |
+| --- |----------------------------------------------------------------------------------------------------------------|
+| `field` | The only required field, specifies the name of the column in the data source to use                           |
+| `displayName` | Sets the label displayed in the chart                                                                  |
+| `agg` |  Defines the aggregation function applied to the column: supported aggregations include `AVG`, `COUNT`, `MAX`, `MIN`, `SUM` |
+| `graphStyle` | Indicates the style of the graph displayed: supported styles include `LINES`, `BARS`, `POINTS`                          |
+| `columnAlignment` | Specifies the alignment of the column in the table: supported alignments include `LEFT`, `RIGHT`, `CENTER`               |
+
+
+You can also use the `where` property to set conditions that filter the result set before displaying it in the chart. Filters can apply to any column in the data source. For shared logic, use the `AND` operator in the `where` property to combine several conditions. If multiple conditions are needed with different logic, use the `type: OR` property.
+
+Available filter types include:
+- `CONTAINS`
+- `ENDS_WITH`
+- `EQUAL_TO`
+- `GREATER_THAN`
+- `GREATER_THAN_OR_EQUAL_TO`
+- `IN`
+- `IS_FALSE`
+- `IS_NOT_NULL`
+- `IS_NULL`
+- `IS_TRUE`
+- `LESS_THAN`
+- `LESS_THAN_OR_EQUAL_TO`
+- `NOT_EQUAL_TO`
+- `NOT_IN`
+- `OR`
+- `REGEX`
+- `STARTS_WITH`.
+
+Available field types include the following columns:
+- `ATTEMPT_NUMBER`
+- `DATE`
+- `DURATION`
+- `END_DATE`
+- `EXECUTION_ID`
+- `FLOW_ID`
+- `FLOW_REVISION`
+- `ID`
+- `LABELS`
+- `LEVEL`
+- `MESSAGE`
+- `NAME`
+- `NAMESPACE`
+- `START_DATE`
+- `STATE`
+- `TASK_ID`
+- `TASK_RUN_ID`
+- `TRIGGER_ID`
+- `TYPE`
+- `VALUE`.
+
+Note that some of the above are reserved only for specific types of `data` e.g., the `LEVEL` column is only available for `type: io.kestra.plugin.core.dashboard.data.Logs`.