We can use **OAuth2** to build that with **FastAPI**.

But let's save you the time of reading the full long specification just to find those little pieces of information you need.

Let's use the tools provided by **FastAPI** to handle security.

## How it looks { #how-it-looks }

Let's first just use the code and see how it works, and then we'll come back to understand what's happening.

## Create `main.py` { #create-main-py }

import org.codelibs.core.stream.StreamUtil;
import org.codelibs.fess.crawler.Constants;

/**
 * The FormScheme class implements the AuthScheme interface to provide
 * form-based authentication for HTTP clients. It handles the process of
 * obtaining a token and logging in using the provided credentials.
 *
 * <p>This class supports both GET and POST methods for token and login
 * requests. It also allows for the replacement of placeholders in URLs and

      return proxiesOrNull.toImmutableList()
    }

    connectionUser.proxySelectStart(url)
    proxies = selectProxies()
    nextProxyIndex = 0
    connectionUser.proxySelectEnd(url, proxies)
  }

  /** Returns true if there's another proxy to try. */
  private fun hasNextProxy(): Boolean = nextProxyIndex < proxies.size

  /** Returns the next proxy to try. May be PROXY.NO_PROXY but never null. */

  public static final byte SI = 15;

  /**
   * Data Link Escape: A communication control character which will change the meaning of a limited
   * number of contiguously following characters. It is used exclusively to provide supplementary
   * controls in data communication networks.
   *
   * @since 8.0
   */
  public static final byte DLE = 16;

  /**

   * set will be backed by an {@link EnumSet}.
   *
   * <p>The iteration order of the returned set follows the enum's iteration order, not the order in
   * which the elements are provided to the method.
   *
   * @param anElement one of the elements the set should contain
   * @param otherElements the rest of the elements the set should contain

    check_success: (Function) function that takes one argument and returns a
      boolean. Should return True if the value provided is considered valid. May
      contain a complex error message if error_msg does not provide enough
      information. In that case, set suppress_default_error to True.
    error_msg: (String) String with one and only one '%s'. Formatted with each

   * the capacity, it is doubled in size unless some other thread
   * holds the lock. If a hashed slot is empty, and lock is
   * available, a new Cell is created. Otherwise, if the slot
   * exists, a CAS is tried.  Retries proceed by "double hashing",
   * using a secondary hash (Marsaglia XorShift) to try to find a
   * free slot.
   *
   * The table size is capped because, when there are more threads

 * majority of usages of {@code Ordering} can be written using only built-in JDK APIs. This class is
 * intended to "fill the gap" and provide those features of {@code Ordering} not already provided by
 * the JDK.
 *
 * @since 21.0
 * @author Louis Wasserman
 */
@GwtCompatible
public final class Comparators {
  private Comparators() {}

  /**

import java.net.URI
import okhttp3.internal.format

class RecordingProxySelector : ProxySelector() {
  @JvmField val proxies = mutableListOf<Proxy>()

  val requestedUris = mutableListOf<URI>()
  val failures = mutableListOf<String>()

  override fun select(uri: URI): List<Proxy> {
    requestedUris.add(uri)
    return proxies
  }

  fun assertRequests(vararg expectedUris: URI?) {

import java.util.Map;
import org.jspecify.annotations.Nullable;

/**
 * A {@link UnicodeEscaper} that uses an array to quickly look up replacement characters for a given
 * code point. An additional safe range is provided that determines whether code points without
 * specific replacements are to be considered safe and left unescaped or should be escaped in a
 * general way.
 *