docs(v1): add comprehensive application configuration reference

docs/content/en/docs-v1.0.x/user-guide/managing-application/configuration-reference.md

@@ -6,7 +6,77 @@ description: >
   Learn about all the configurable fields in the application configuration file.
 ---
 
->**Note:**
->PipeCD v1 documentation is still a work in progress. We are updating this configuration reference.
-> Until then, [see configurable fields for the application configuration file for v0.55](../../../docs-v0.55.x/user-guide/configuration-reference.md), and if you have any questions, [reach out to us](../../../../../../README.md#community-and-development) using one of our communication channels.
->Happy PipeCDing!
+This page describes all configurable fields in the application configuration for PipeCD v1.
+
+Unlike previous versions, PipeCD v1 unifies all application types under a single `Application` kind. The specific platform (Kubernetes, Terraform, Cloud Run, etc.) is now defined using a platform label.
+
+### Example `app.config`
+
+```yaml
+apiVersion: pipecd.dev/v1beta1
+kind: Application
+labels:
+  pipecd.dev/platform: KUBERNETES # Or TERRAFORM, CLOUDRUN, LAMBDA, ECS
+spec:
+  name: my-app
+  description: "My unified v1 application"
+  plugins: {}
+  pipeline: {}
+```
+
+## Application Configuration
+
+| Field | Type | Description | Required |
+| --- | --- | --- | --- |
+| `apiVersion` | string | `pipecd.dev/v1beta1` | Yes |
+| `kind` | string | `Application` | Yes |
+| `labels` | map[string]string | Additional attributes to identify applications. Must include the `pipecd.dev/platform` label to specify the platform type. | Yes |
+| `spec.name` | string | The application name. | Yes |
+| `spec.description` | string | Notes on the Application. | No |
+| `spec.planner` | DeploymentPlanner | Configuration used while planning the deployment. | No |
+| `spec.commitMatcher` | DeploymentCommitMatcher | Forcibly use QuickSync or Pipeline when commit message matched the specified pattern. | No |
+| `spec.pipeline` | Pipeline | Pipeline definition for progressive delivery. | No |
+| `spec.trigger` | Trigger | Configuration used to determine if a new deployment should be triggered. | No |
+| `spec.postSync` | PostSync | Extra actions to execute once the deployment is triggered. | No |
+| `spec.timeout` | duration | The maximum length of time to execute deployment before giving up. Default is `6h`. | No |
+| `spec.encryption` | SecretEncryption | List of encrypted secrets and targets that should be decoded before using. | No |
+| `spec.attachment` | Attachment | List of files that should be attached to application manifests before using. | No |
+| `spec.notification` | DeploymentNotification | Additional configuration for sending notifications to external services. | No |
+| `spec.eventWatcher` | []EventWatcherConfig | List of the configurations for the event watcher. | No |
+| `spec.driftDetection` | [DriftDetection](#driftdetection) | Configuration for drift detection. | No |
+| `spec.plugins` | map[string]any | List of the configurations for plugins. This field is plugin-specific. | No |
+
+*(Note: The `spec.plugins` structures depend on the value of the `pipecd.dev/platform` label. See the specific Plugin documentation for deeper fields).*
+
+## DriftDetection
+
+| Field | Type | Description | Required |
+| --- | --- | --- | --- |
+| `ignoreFields` | []string | List of `apiVersion:kind:namespace:name#fieldPath` to ignore in diffs. | No |
+
+## Planner
+
+| Field | Type | Description | Required |
+| --- | --- | --- | --- |
+| `alwaysUsePipeline` | bool | Whether to always use the pipeline for deployment instead of a QuickSync. | No |
+| `autoRollback` | bool | Whether to automatically rollback to the previous state when the deployment fails. | No |
+
+## Pipeline
+
+| Field | Type | Description | Required |
+| --- | --- | --- | --- |
+| `stages` | []PipelineStage | List of stages to be executed sequentially during the deployment pipeline. | Yes |
+
+## Trigger
+
+| Field | Type | Description | Required |
+| --- | --- | --- | --- |
+| `onCommit` | OnCommit | Configuration for triggering deployments upon new commits. | No |
+| `onCommand` | OnCommand | Configuration for triggering deployments via manual command. | No |
+| `onOutOfSync` | OnOutOfSync | Configuration for triggering deployments when drift is detected. | No |
+
+## PostSync
+
+| Field | Type | Description | Required |
+| --- | --- | --- | --- |
+| `chain` | []PostSyncPlugin | List of plugins or tasks to execute after a successful synchronization. | Yes |