@Nullable
    default AggregatedBodyPart field(String name) {
        requireNonNull(name, "name");
        return bodyParts().stream()
                          .filter(part -> name.equals(part.name()))
                          .findFirst()
                          .orElse(null);
    }
Returns the first body part identified by the given control name. The control
name is the {@code name} parameter of the {@code "content-disposition"}
header for a body part with disposition type {@code form-data}.

@param name control name
@return the {@link BodyPart} of the control name, or {@code null} if not present.
core/src/main/java/com/linecorp/armeria/common/multipart/AggregatedMultipart.java