FINERACT-2830: Correct template OpenAPI response schemas

[swaran21]

Description

FINERACT-2830 corrects the OpenAPI response schemas for:

• GET /v1/templates/template
• GET /v1/templates/{templateId}/template

Both resource methods return TemplateDetailsData, but their OpenAPI annotations previously declared TemplateData.
This change updates the two response annotations to TemplateDetailsData.
The generated OpenAPI specification now correctly exposes:

• entities as an array
• types as an array
• template as nested TemplateData

No runtime behavior, business logic, database behavior, or API response payload has changed.

CQRS consideration

I considered the CQRS migration scope for this issue.
The affected operations are read-only GET endpoints, and this ticket currently concerns correcting their OpenAPI response schemas. Therefore, this PR does not introduce command-processing changes without confirming a specific migration target with the maintainer.
I am happy to discuss whether a template write operation should be migrated to the CQRS infrastructure as a separate or follow-up contribution.

Verification

• Ran :fineract-provider:test --tests org.apache.fineract.template.api.TemplatesApiResourceTest
• Ran :fineract-provider:resolve
• Verified both operations in the generated OpenAPI specification reference #/components/schemas/TemplateDetailsData

The client OpenAPI validation currently reports missing default response descriptions for these two operations. Those descriptions were absent before this schema correction. I will follow maintainer guidance on whether they belong in this ticket.

Checklist

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