Add Activepieces integration for workflow automation

- Add Activepieces fork with SmoothSchedule custom piece
- Create integrations app with Activepieces service layer
- Add embed token endpoint for iframe integration
- Create Automations page with embedded workflow builder
- Add sidebar visibility fix for embed mode
- Add list inactive customers endpoint to Public API
- Include SmoothSchedule triggers: event created/updated/cancelled
- Include SmoothSchedule actions: create/update/cancel events, list resources/services/customers

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

activepieces-fork/docs/build-pieces/piece-reference/authentication.mdx

@@ -0,0 +1,133 @@
+---
+title: "Piece Auth"
+description: "Learn about piece authentication"
+icon: 'key'
+---
+
+Piece authentication is used to gather user credentials and securely store them for future use in different flows.
+The authentication must be defined as the `auth` parameter in the `createPiece`, `createTrigger`, and `createAction` functions. 
+
+This requirement ensures that the type of authentication can be inferred correctly in triggers and actions.
+
+<Warning>
+The auth parameter for `createPiece`, `createTrigger`, and `createAction` functions can take an array, but you cannot have more than one auth property of the same type, i.e two OAUTH2 properties.
+</Warning>
+
+### Secret Text
+
+This authentication collects sensitive information, such as passwords or API keys. It is displayed as a masked input field.
+
+**Example:**
+
+```typescript
+PieceAuth.SecretText({
+    displayName: 'API Key',
+    description: 'Enter your API key',
+    required: true,
+    // Optional Validation
+    validate: async ({auth}) => {
+        if(auth.startsWith('sk_')){
+            return {
+                valid: true,
+            }
+        }
+        return {
+            valid: false,
+            error: 'Invalid Api Key'
+        }
+    }
+})
+```
+
+### Username and Password
+
+This authentication collects a username and password as separate fields.
+
+**Example:**
+
+```typescript
+PieceAuth.BasicAuth({
+    displayName: 'Credentials',
+    description: 'Enter your username and password',
+    required: true,
+    username: {
+        displayName: 'Username',
+        description: 'Enter your username',
+    },
+    password: {
+        displayName: 'Password',
+        description: 'Enter your password',
+    },
+    // Optional Validation
+    validate: async ({auth}) => {
+        if(auth){
+            return {
+                valid: true,
+            }
+        }
+        return {
+            valid: false,
+            error: 'Invalid Api Key'
+        }
+    }
+})
+```
+
+### Custom
+
+This authentication allows for custom authentication by collecting specific properties, such as a base URL and access token.
+
+**Example:**
+
+```typescript
+PieceAuth.CustomAuth({
+    displayName: 'Custom Authentication',
+    description: 'Enter custom authentication details',
+    props: {
+        base_url: Property.ShortText({
+            displayName: 'Base URL',
+            description: 'Enter the base URL',
+            required: true,
+        }),
+        access_token: PieceAuth.SecretText({
+            displayName: 'Access Token',
+            description: 'Enter the access token',
+            required: true
+        })
+    },
+    // Optional Validation
+    validate: async ({auth}) => {
+        if(auth){
+            return {
+                valid: true,
+            }
+        }
+        return {
+            valid: false,
+            error: 'Invalid Api Key'
+        }
+    },
+    required: true
+})
+```
+
+### OAuth2
+
+This authentication collects OAuth2 authentication details, including the authentication URL, token URL, and scope.
+
+**Example:**
+
+```typescript
+PieceAuth.OAuth2({
+    displayName: 'OAuth2 Authentication',
+    grantType: OAuth2GrantType.AUTHORIZATION_CODE,
+    required: true,
+    authUrl: 'https://example.com/auth',
+    tokenUrl: 'https://example.com/token',
+    scope: ['read', 'write']
+})
+```
+
+<Tip>
+Please note `OAuth2GrantType.CLIENT_CREDENTIALS` is also supported for service-based authentication.
+</Tip>