Add some documentation

Author: moliware

README.md

@@ -27,6 +27,56 @@ You can run cerebro listening on a different host and port(defaults to 0.0.0.0:9
 bin/cerebro -Dhttp.port=1234 -Dhttp.address=127.0.0.1
 ```
 
+#### LDAP config
+
+LDAP can be configured using environment variables. If you typically run cerebro using docker,
+you can pass a file with all the env vars. The file would look like:
+
+```bash
+# Set it to ldap to activate ldap authorization
+AUTH_TYPE=ldap
+
+# Your ldap url
+LDAP_URL=ldap://exammple.com:389
+
+LDAP_BASE_DN=OU=users,DC=example,DC=com
+
+# Usually method should  be "simple" otherwise, set it to the SASL mechanisms
+LDAP_METHOD=simple
+
+# user-template executes a string.format() operation where
+# username is passed in first, followed by base-dn. Some examples
+#  - %s => leave user untouched
+#  - %s@domain.com => append "@domain.com" to username
+#  - uid=%s,%s => usual case of OpenLDAP
+LDAP_USER_TEMPLATE=%s@example.com
+
+# User identifier that can perform searches
+LDAP_BIND_DN=admin@example.com
+LDAP_BIND_PWD=adminpass
+
+# Group membership settings (optional)
+
+# If left unset LDAP_BASE_DN will be used
+# LDAP_GROUP_BASE_DN=OU=users,DC=example,DC=com
+
+# Attribute that represent the user, for example uid or mail
+# LDAP_USER_ATTR=mail
+
+# Filter that tests membership of the group. If this property is empty then there is no group membership check
+# AD example => memberOf=CN=mygroup,ou=ouofthegroup,DC=domain,DC=com
+# OpenLDAP example => CN=mygroup
+# LDAP_GROUP=memberOf=memberOf=CN=mygroup,ou=ouofthegroup,DC=domain,DC=com
+
+```
+
+You can the pass this file as argument using:
+
+```bash
+ docker run -p 9000:9000 --env-file env-ldap  lmenezes/cerebro
+```
+
+
 #### Other settings
 
 Other settings are exposed through the **conf/application.conf** file found on the application directory.