Specify explicit REST formats

Always specify explicit request formats in REST API tests rather than relying on default behaviors. This includes:

1. Set appropriate Content-Type headers (typically application/json for REST APIs)
2. Define explicit query parameters that clearly test intended functionality

Without proper format specifications, tests may fail unexpectedly or test incorrect behaviors. For example, missing Content-Type headers might cause an endpoint to default to different formats like cbor instead of JSON:

- do:
    headers:
      Content-Type: application/json  # Explicitly specify format
    index:
      index: test
      id: 1
      body: { "field": "value" }

Similarly, when testing query parameters, be explicit about the expected behavior rather than using generic queries that might not fully test the intended functionality:

retriever:
  standard:
    query:
      match_none: {}  # Explicitly testing empty results case

This practice improves test reliability and clarity by making the expected request format visible and intentional rather than implicit.