[DS-GW] Add Gateway data-source

[Or167]

📝 Description

When I am automating and managing data analytics infrastructure using Microsoft Fabric across multiple environments,
I want to get details of Gateways as code in Terraform.
So, I can consistently and securely manage my data connectivity resources, ensure repeatable deployments, and streamline updates in a single Infrastructure-as-Code workflow.

🔬 Details / References

Resource Name: fabric_gateway
API documentation:
Create Gateway: https://learn.microsoft.com/en-us/rest/api/fabric/core/gateways/create-gateway?tabs=HTTP
Delete Gateway: https://learn.microsoft.com/en-us/rest/api/fabric/core/gateways/delete-gateway?tabs=HTTP
Get Gateway: https://learn.microsoft.com/en-us/rest/api/fabric/core/gateways/get-gateway?tabs=HTTP
Update Gateway: https://learn.microsoft.com/en-us/rest/api/fabric/core/gateways/update-gateway?tabs=HTTP

🚧 Potential Terraform Configuration / Desired Solution

# Get Gateway details by name
data "fabric_gateway" "example_by_name" {
  display_name = "example"
}
 
# Get Gateway details by id
data "fabric_gateway" "example_by_id" {
  id           = "11111111-1111-1111-1111-111111111111"
}
 

📎 Additional context

No response

☑️ Acceptance Criteria

No response

✅ Definition of Done

• Data Transfer Objects (DTOs)
• Data-Source Implementation
• Data-Source Added to Provider
• Unit Tests for Happy path
• Unit Tests for Error path
• Acceptance Tests
• Example in the ./examples folder
• Schema documentation in code
• Updated auto-generated provider docs with task docs

🔰 Code of Conduct

• I agree to follow this project's Code of Conduct.