Add limits on name values

Fixes: https://pagure.io/koji/issue/2117

docs/source/hub_conf.rst

@@ -0,0 +1,51 @@
+hub.conf
+--------
+hub.conf is a standard .ini-like configuration file. Its main section is
+called ``[hub]`` and contains the following options. They can occur anywhere.
+
+Incomplete document
+^^^^^^^^^^^^^^^^^^^
+
+This document is a stub and does not cover all options.
+Work to complete this document is tracked in `Issue 3073 <https://pagure.io/koji/issue/3073>`_
+
+The old :doc:`Server HOW TO <server_howto>` doc also describes some hub configuration options.
+
+Name verification
+^^^^^^^^^^^^^^^^^
+Currently we have two groups for name verification:
+ - internal names
+ - user names
+
+Group internal names is currently used for:
+ - archive type
+ - btype
+ - channel
+ - external repo
+ - group
+ - host
+ - kerberos
+ - permission
+ - tag
+ - target
+ - volume
+
+Group user names is currently used for:
+ - user
+ - host
+
+Host names are listed in both groups because hosts always have an associated user entry.
+
+.. glossary::
+    MaxNameLengthInternal = 256
+        Set length of internal names. By default there is allowed length set up to 256.
+        When length is set up to 0, length verifying is disabled.
+
+    RegexNameInternal = ^[A-Za-z0-9/_.+-]+$
+        Set regex for verify an internal names. When regex string is empty, verifying
+        is disabled.
+
+    RegexUserName = ^[A-Za-z0-9/_.@-]+$
+        Set regex for verify a user name and kerberos. User name and kerberos have
+        in default set up allowed '@' and '/' chars on top of basic name regex
+        for internal names. When regex string is empty, verifying is disabled.

docs/source/index.rst

@@ -41,6 +41,7 @@ Contents
     signing
     database_howto
     kojid_conf
+    hub_conf
     using_the_koji_build_system
     setting_rpm_macros
     profiles

docs/source/server_howto.rst

@@ -777,6 +777,8 @@ override all these values. So, you can use e.g.
 ``/etc/koji-hub/hub.conf.d/secret.conf`` for sensitive values. Typical usecase
 for separate config is :doc:`policy <defining_hub_policies>` configuration file.
 
+Doc page about hub options in :doc:`Hub conf <hub_conf>`. (Currently in progress).
+
 Authentication Configuration
 ----------------------------