Improve test coverage for example/http-server-using-redis

[AkshayCdra]

Description:

• Extract cache warmup logic into standalone function for better testability
• Add unit tests for Redis GET handler

Checklist:

• I have formatted my code using goimport and golangci-lint.
• I have reviewed the code comments and documentation for clarity.

[aryanmehrotra]

code should not be changed for adding tests

[Umang01-hash]

@AkshayCdr the coverage of examples/http-server-using-redis was 94.6% previously and after this PR also it is same 94.6%. How is this a improvement in coverage?

In the main.go:

		err := ctx.Redis.Set(ctx, cacheKey, cacheValue, 0).Err()
		if err != nil {
			ctx.Logger.Errorf("Failed to warm up cache: %v", err)
			return err // Return the error to halt startup if caching fails.
		}

Only this part is uncovered currenly, if we can cover it then it will be an improvement for sure!