api: add Integration test cases

[ashwiniag]

closes #44

Introduces

• fixes on API responses, it returns
  a. list of integration objects only
  b. returns updated objects as response on PUT instead of key word updated
• improves error handling
• adds test cases

As follows

GET /integrations/{id}

Test Case	Description	Adds Error Handling
Valid ID	Verifies response for a valid integration ID. ✅
Invalid UUID Format	Ensures malformed UUIDs return appropriate error. ✅	400 Bad Request ✅
Non-existent ID	Ensures non-existent IDs return appropriate error. ✅	404 Not Found ✅

GET /integrations

Test Case	Description	Adds Error Handling
Valid Request	Verifies all integrations are listed correctly. ✅
Empty Database	Verifies response when no integrations exist. ✅

POST /integrations

Test Case	Description	Adds Error Handling
Valid Input	Ensures integration is created successfully. ✅
Missing Fields	Verifies name or type is required. ✅	400 Bad Request ✅
Duplicate Name	Ensures duplicates return appropriate error. ✅	409 Conflict ✅
Invalid Type	Verifies validation for non-existent integration types. ✅	Pending implementation for later, post IntegrationTypes
Empty Config	Ensures creation works with an empty configuration. ✅	To be changed later

PUT /integrations/{id}

Test Case	Description	Adds Error Handling
Valid Update	Ensures integration is updated successfully. ✅
Partial Update	Verifies update works when only one field is provided. ✅
Invalid UUID Format	Ensures malformed UUIDs return appropriate error.	400 Bad Request ✅
Non-existent ID	Ensures non-existent IDs return appropriate error. ✅	404 Not Found ✅
No Changes	Verifies no update when no fields are provided. ✅

[scriptnull]

Instead of organising tests like

├── get.go
├── post.go
├── put.go
└── tests
    ├── get_test.go
    ├── post_test.go
    └── put_test.go

Let us organise it like

├── get.go
├── get_test.go
├── post.go
├── post_test.go
├── put.go
└── put_test.go

In Go, it is usually preferred to have tests side by side with a _test.go suffix.