Add example of running Jaeger UI behind reverse proxy

Signed-off-by: Yuri Shkuro <github@ysh.us>

examples/reverse-proxy/README.md

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+# reverse-proxy example
+
+This example illustrates how Jaeger UI can be run behind a reverse proxy under a different URL prefix.
+
+Start the servers:
+
+```sh
+cd examples/reverse-proxy
+docker compose up
+```
+
+Jaeger UI can be accesssed at http://localhost:18080/jaeger/prefix .

examples/reverse-proxy/docker-compose.yml

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+version: '3.7'
+
+services:
+  jaeger:
+    image: jaegertracing/all-in-one:latest
+    ports:
+      - "16686:16686"  # Jaeger UI
+      - "4317:4317"    # Collector, OpenTelemetry gRPC
+      - "4318:4318"    # Collector, OpenTelemetry gRPC
+    environment:
+      # This tells Jaeger that it should run the UI with a given prefix.
+      QUERY_BASE_PATH: /jaeger/prefix
+    networks:
+      - proxy-net
+
+  httpd:
+    image: httpd:latest
+    ports:
+      - "18080:80"
+    volumes:
+      - ./httpd.conf:/usr/local/apache2/conf/httpd.conf
+    depends_on:
+      - jaeger
+    networks:
+      - proxy-net
+
+networks:
+  proxy-net:

examples/reverse-proxy/httpd.conf

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+ServerRoot "/usr/local/apache2"
+
+Listen 80
+
+LoadModule mpm_event_module modules/mod_mpm_event.so
+LoadModule proxy_module modules/mod_proxy.so
+LoadModule proxy_http_module modules/mod_proxy_http.so
+# some of the modules below may not be needed
+LoadModule authn_file_module modules/mod_authn_file.so
+LoadModule authn_core_module modules/mod_authn_core.so
+LoadModule authz_host_module modules/mod_authz_host.so
+LoadModule authz_groupfile_module modules/mod_authz_groupfile.so
+LoadModule authz_user_module modules/mod_authz_user.so
+LoadModule authz_core_module modules/mod_authz_core.so
+LoadModule access_compat_module modules/mod_access_compat.so
+LoadModule auth_basic_module modules/mod_auth_basic.so
+LoadModule reqtimeout_module modules/mod_reqtimeout.so
+LoadModule filter_module modules/mod_filter.so
+LoadModule mime_module modules/mod_mime.so
+LoadModule log_config_module modules/mod_log_config.so
+LoadModule env_module modules/mod_env.so
+LoadModule headers_module modules/mod_headers.so
+LoadModule setenvif_module modules/mod_setenvif.so
+LoadModule version_module modules/mod_version.so
+LoadModule unixd_module modules/mod_unixd.so
+LoadModule status_module modules/mod_status.so
+LoadModule autoindex_module modules/mod_autoindex.so
+LoadModule dir_module modules/mod_dir.so
+LoadModule alias_module modules/mod_alias.so
+LoadModule rewrite_module modules/mod_rewrite.so
+
+# Note that the prefix is used in both the proxy and the backend URLs.
+ProxyPass "/jaeger/prefix" "http://jaeger:16686/jaeger/prefix"
+ProxyPassReverse "/jaeger/prefix" "http://jaeger:16686/jaeger/prefix"
+
+ErrorLog /proc/self/fd/2
+LogLevel info
+<IfModule log_config_module>
+    #
+    # The following directives define some format nicknames for use with
+    # a CustomLog directive (see below).
+    #
+    LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
+    LogFormat "%h %l %u %t \"%r\" %>s %b" common
+
+    <IfModule logio_module>
+      # You need to enable mod_logio.c to use %I and %O
+      LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\" %I %O" combinedio
+    </IfModule>
+
+    #
+    # The location and format of the access logfile (Common Logfile Format).
+    # If you do not define any access logfiles within a <VirtualHost>
+    # container, they will be logged here.  Contrariwise, if you *do*
+    # define per-<VirtualHost> access logfiles, transactions will be
+    # logged therein and *not* in this file.
+    #
+    CustomLog /proc/self/fd/1 common
+
+    #
+    # If you prefer a logfile with access, agent, and referer information
+    # (Combined Logfile Format) you can use the following directive.
+    #
+    #CustomLog "logs/access_log" combined
+</IfModule>