httpx.post(callback_url, json={"description": "Invoice paid", "paid": True})
```

But possibly the most important part of the callback is making sure that your API user (the external developer) implements the *external API* correctly, according to the data that *your API* is going to send in the request body of the callback, etc.

 * including user authentication, validation, message handling, and access context management.
 * It extends LastaFlute's TypicalAction and implements validation and HTML path interfaces.
 *
 * @since 1.0
 */
public abstract class FessBaseAction extends TypicalAction // has several interfaces for direct use
        implements LaValidatable<FessMessages>, FessHtmlPath {

    /**
     * Default constructor.
     */
    public FessBaseAction() {

  public static short fromBytes(byte b1, byte b2) {
    return (short) ((b1 << 8) | (b2 & 0xFF));
  }

  private static final class ShortConverter extends Converter<String, Short>
      implements Serializable {
    static final Converter<String, Short> INSTANCE = new ShortConverter();

    @Override
    protected Short doForward(String value) {
      return Short.decode(value);
    }

  public static short fromBytes(byte b1, byte b2) {
    return (short) ((b1 << 8) | (b2 & 0xFF));
  }

  private static final class ShortConverter extends Converter<String, Short>
      implements Serializable {
    static final Converter<String, Short> INSTANCE = new ShortConverter();

    @Override
    protected Short doForward(String value) {
      return Short.decode(value);
    }

/**
 * Base class for services that can implement {@link #startUp}, {@link #run} and {@link #shutDown}
 * methods. This class uses a single thread to execute the service; consider {@link AbstractService}
 * if you would like to manage any threading manually.
 *
 * @author Jesse Wilson
 * @since 1.0
 */
@GwtIncompatible
@J2ktIncompatible
public abstract class AbstractExecutionThreadService implements Service {

	}
}

// ErrNotImplemented when a functionality is not implemented
var ErrNotImplemented = errors.New("not implemented")

// ReadFrom implements support for calling internal io.ReaderFrom implementations
// returns an error if the underlying ResponseWriter does not implement io.ReaderFrom
func (lrw *ResponseRecorder) ReadFrom(r io.Reader) (int64, error) {
	if lrw.ReaderFrom != nil {
		n, err := lrw.ReaderFrom.ReadFrom(r)

import java.io.Serializable;
import java.util.List;

import org.codelibs.fess.Constants;
import org.codelibs.fess.util.ComponentUtil;

/**
 * The pager for access token.
 */
public class AccessTokenPager implements Serializable {
    private static final long serialVersionUID = 1L;

    /**
     * Default constructor.
     */
    public AccessTokenPager() {
        // nothing
    }

    /**

import org.codelibs.fess.util.ComponentUtil;

/**
 * Pager class for character mapping management with pagination support.
 * Provides pagination functionality for character mapping lists.
 */
public class CharMappingPager implements Serializable {

    private static final long serialVersionUID = 1L;

    /** Total number of records across all pages. */
    private int allRecordCount;

    /** Total number of pages available. */

package org.codelibs.fess.app.pager;

import java.io.Serializable;
import java.util.List;

import org.codelibs.fess.util.ComponentUtil;

/**
 * Pager for path mapping.
 */
public class PathMapPager implements Serializable {

    /**
     * Default constructor.
     */
    public PathMapPager() {
        // Default constructor
    }

    private static final long serialVersionUID = 1L;

package org.codelibs.fess.app.pager;

import java.io.Serializable;
import java.util.List;

import org.codelibs.fess.util.ComponentUtil;

/**
 * Pager for role management.
 *
 */
public class RolePager implements Serializable {

    /**
     * Constructor.
     */
    public RolePager() {
        super();
    }

    private static final long serialVersionUID = 1L;

    /**