feat: Add DeepSeek Chat Model node (#12873)

packages/@n8n/nodes-langchain/credentials/DeepSeekApi.credentials.ts

@@ -0,0 +1,47 @@
+import type {
+	IAuthenticateGeneric,
+	ICredentialTestRequest,
+	ICredentialType,
+	INodeProperties,
+} from 'n8n-workflow';
+
+export class DeepSeekApi implements ICredentialType {
+	name = 'deepSeekApi';
+
+	displayName = 'DeepSeek';
+
+	documentationUrl = 'deepseek';
+
+	properties: INodeProperties[] = [
+		{
+			displayName: 'API Key',
+			name: 'apiKey',
+			type: 'string',
+			typeOptions: { password: true },
+			required: true,
+			default: '',
+		},
+		{
+			displayName: 'Base URL',
+			name: 'url',
+			type: 'hidden',
+			default: 'https://api.deepseek.com',
+		},
+	];
+
+	authenticate: IAuthenticateGeneric = {
+		type: 'generic',
+		properties: {
+			headers: {
+				Authorization: '=Bearer {{$credentials.apiKey}}',
+			},
+		},
+	};
+
+	test: ICredentialTestRequest = {
+		request: {
+			baseURL: '={{ $credentials.url }}',
+			url: '/models',
+		},
+	};
+}