Add Autosend node with Mail and Contact resources

Implement n8n node for Autosend API with support for:
- Mail resource: Send single and bulk emails with template or custom content
- Contact resource: Create/update contacts (upsert) and get contacts by ID or email
- API key authentication
- Declarative routing following n8n best practices
- Full TypeScript support with proper typing
- Passing all linting checks

nodes/Autosend/resources/contact/upsert.ts

@@ -0,0 +1,142 @@
+import type { INodeProperties } from 'n8n-workflow';
+
+export const upsertOperation: INodeProperties[] = [
+	{
+		displayName: 'Email',
+		name: 'email',
+		type: 'string',
+		required: true,
+		placeholder: 'contact@example.com',
+		default: '',
+		displayOptions: {
+			show: {
+				resource: ['contact'],
+				operation: ['upsert'],
+			},
+		},
+		routing: {
+			send: {
+				type: 'body',
+				property: 'email',
+			},
+		},
+		description: 'The email address of the contact',
+	},
+	{
+		displayName: 'User ID',
+		name: 'userId',
+		type: 'string',
+		default: '',
+		displayOptions: {
+			show: {
+				resource: ['contact'],
+				operation: ['upsert'],
+			},
+		},
+		routing: {
+			send: {
+				type: 'body',
+				property: 'userId',
+			},
+		},
+		description: 'External user ID from your system',
+	},
+	{
+		displayName: 'Additional Fields',
+		name: 'additionalFields',
+		type: 'collection',
+		placeholder: 'Add Field',
+		default: {},
+		displayOptions: {
+			show: {
+				resource: ['contact'],
+				operation: ['upsert'],
+			},
+		},
+		options: [
+			{
+				displayName: 'Company',
+				name: 'company',
+				type: 'string',
+				default: '',
+				routing: {
+					send: {
+						type: 'body',
+						property: 'company',
+					},
+				},
+				description: 'Company name',
+			},
+			{
+				displayName: 'Custom Fields (JSON)',
+				name: 'customFields',
+				type: 'json',
+				default: '{}',
+				routing: {
+					send: {
+						type: 'body',
+						property: 'customFields',
+						preSend: [
+							async function (this, requestOptions) {
+								const customFieldsStr = this.getNodeParameter(
+									'additionalFields.customFields',
+									'',
+								) as string;
+								if (customFieldsStr) {
+									try {
+										const customFields = JSON.parse(customFieldsStr);
+										requestOptions.body = requestOptions.body || {};
+										(requestOptions.body as Record<string, unknown>).customFields = customFields;
+									} catch {
+										throw new Error('Custom Fields must be valid JSON');
+									}
+								}
+								return requestOptions;
+							},
+						],
+					},
+				},
+				description: 'Additional custom fields as a JSON object',
+			},
+			{
+				displayName: 'First Name',
+				name: 'firstName',
+				type: 'string',
+				default: '',
+				routing: {
+					send: {
+						type: 'body',
+						property: 'firstName',
+					},
+				},
+				description: 'First name of the contact',
+			},
+			{
+				displayName: 'Last Name',
+				name: 'lastName',
+				type: 'string',
+				default: '',
+				routing: {
+					send: {
+						type: 'body',
+						property: 'lastName',
+					},
+				},
+				description: 'Last name of the contact',
+			},
+			{
+				displayName: 'Phone',
+				name: 'phone',
+				type: 'string',
+				default: '',
+				routing: {
+					send: {
+						type: 'body',
+						property: 'phone',
+					},
+				},
+				description: 'Phone number of the contact',
+			},
+		],
+	},
+];