Merge pull request #1300 from eloycoto/liquidLog

Doc: Add liquid examples

Author: eguzki

doc/liquid_conditions.md

@@ -0,0 +1,67 @@
+# Liquid conditions examples
+
+You can use Liquid to configure conditions applicable across multiple policies to <insert_purpose>
+of conditions that can be used across multiple policies
+
+
+## Headers
+
+### Header is not present
+
+Condition passes if the  'Backend' header is sent and it's staging
+
+```
+"condition":{
+   "operations":[
+      {
+         "left":" {% if headers['Backend'] %}{{ headers['Backend'] }}{%else%}Notpresent{%endif%}",
+         "left_type":"liquid",
+         "op":"==",
+         "right":"staging"
+      }
+   ]
+}
+```
+
+If you want to test when the `Backend` header is not present, the condition is as follows:
+
+```
+"condition":{
+   "operations":[
+      {
+         "left":" {% if headers['Backend'] %}IsPresent{%else%}Notpresent{%endif%}",
+         "left_type":"liquid",
+         "op":"==",
+         "right":"Notpresent"
+      }
+   ]
+}
+```
+
+## Numeric operations
+
+Numeric operations require additional steps. By default, all the values on liquid are strings, so you need
+to get any integer before do any operation. Use `minus` or `plus`
+filters along with `0` (zero), and apply the following configuration:
+
+
+```
+"condition":{
+  "operations":[
+    {
+      "left": "{% assign val = headers['version'] | minus:0 %} {%if val < 20 %}PASS{%else%}DENIED{%endif%}",
+      "left_type":"liquid",
+      "op":"==",
+      "right":"PASS"
+    }
+ ]
+}
+```
+
+@TODO: something like a int filter should be added.
+@TODO: default filter should be added too.
+
+
+## Additional examples:
+
+[How to send different headers according to the Application Plan](https://access.redhat.com/solutions/3925031)