feat(pricing/ai): improve billing metered pricing + add pricing on ai chat (#14092)

## TODO:

- [x] display "yearly" or "monthly" wording everywhere it's needed
- [ ] Add button with "downgrade" or "upgrade" to save the change of
credits price + modal to validate
- [x] Add renewal date 
- [ ] Implement
https://docs.stripe.com/billing/subscriptions/subscription-schedules for
`switchFromYearlyToMonthly` and decrease number of credits

packages/twenty-server/src/engine/metadata-modules/agent/agent-execution.service.ts

@@ -7,8 +7,6 @@ import {
   type CoreMessage,
   type CoreUserMessage,
   type FilePart,
-  generateObject,
-  generateText,
   type ImagePart,
   streamText,
   ToolSet,
@@ -30,11 +28,10 @@ import { AgentHandoffToolService } from 'src/engine/metadata-modules/agent/agent
 import { AGENT_CONFIG } from 'src/engine/metadata-modules/agent/constants/agent-config.const';
 import { AGENT_SYSTEM_PROMPTS } from 'src/engine/metadata-modules/agent/constants/agent-system-prompts.const';
 import { type RecordIdsByObjectMetadataNameSingularType } from 'src/engine/metadata-modules/agent/types/recordIdsByObjectMetadataNameSingular.type';
-import { convertOutputSchemaToZod } from 'src/engine/metadata-modules/agent/utils/convert-output-schema-to-zod';
 import { WorkspacePermissionsCacheService } from 'src/engine/metadata-modules/workspace-permissions-cache/workspace-permissions-cache.service';
 import { TwentyORMGlobalManager } from 'src/engine/twenty-orm/twenty-orm-global.manager';
-import { type OutputSchema } from 'src/modules/workflow/workflow-builder/workflow-schema/types/output-schema.type';
 import { streamToBuffer } from 'src/utils/stream-to-buffer';
+import { AIBillingService } from 'src/engine/core-modules/ai/services/ai-billing.service';
 
 import { AgentToolGeneratorService } from './agent-tool-generator.service';
 import { AgentEntity } from './agent.entity';
@@ -61,6 +58,7 @@ export class AgentExecutionService {
     private readonly workspacePermissionsCacheService: WorkspacePermissionsCacheService,
     private readonly aiModelRegistryService: AiModelRegistryService,
     private readonly agentToolGeneratorService: AgentToolGeneratorService,
+    private readonly aiBillingService: AIBillingService,
     @InjectRepository(AgentEntity)
     private readonly agentRepository: Repository<AgentEntity>,
     @InjectRepository(FileEntity)
@@ -301,66 +299,18 @@ export class AgentExecutionService {
       `Sending request to AI model with ${llmMessages.length} messages`,
     );
 
-    return streamText(aiRequestConfig);
-  }
+    const model = await this.aiModelRegistryService.resolveModelForAgent(agent);
 
-  async executeAgent({
-    agent,
-    schema,
-    userPrompt,
-  }: {
-    agent: AgentEntity | null;
-    context: Record<string, unknown>;
-    schema: OutputSchema;
-    userPrompt: string;
-  }): Promise<AgentExecutionResult> {
-    try {
-      const aiRequestConfig = await this.prepareAIRequestConfig({
-        system: `You are executing as part of a workflow automation. ${agent ? agent.prompt : ''}`,
-        agent,
-        prompt: userPrompt,
-      });
-      const textResponse = await generateText(aiRequestConfig);
+    const stream = streamText(aiRequestConfig);
 
-      if (Object.keys(schema).length === 0) {
-        return {
-          result: { response: textResponse.text },
-          usage: textResponse.usage,
-        };
-      }
-      const output = await generateObject({
-        system: AGENT_SYSTEM_PROMPTS.OUTPUT_GENERATOR,
-        model: aiRequestConfig.model,
-        prompt: `Based on the following execution results, generate the structured output according to the schema:
-
-                 Execution Results: ${textResponse.text}
-
-                 Please generate the structured output based on the execution results and context above.`,
-        schema: convertOutputSchemaToZod(schema),
-      });
-
-      return {
-        result: output.object,
-        usage: {
-          promptTokens:
-            (textResponse.usage?.promptTokens ?? 0) +
-            (output.usage?.promptTokens ?? 0),
-          completionTokens:
-            (textResponse.usage?.completionTokens ?? 0) +
-            (output.usage?.completionTokens ?? 0),
-          totalTokens:
-            (textResponse.usage?.totalTokens ?? 0) +
-            (output.usage?.totalTokens ?? 0),
-        },
-      };
-    } catch (error) {
-      if (error instanceof AgentException) {
-        throw error;
-      }
-      throw new AgentException(
-        error instanceof Error ? error.message : 'Agent execution failed',
-        AgentExceptionCode.AGENT_EXECUTION_FAILED,
+    stream.usage.then((usage) => {
+      this.aiBillingService.calculateAndBillUsage(
+        model.modelId,
+        usage,
+        workspace.id,
       );
-    }
+    });
+
+    return stream;
   }
 }