Introduce `properties` for consent purposes

[nirmal070125]

• WSO2 IS has a requirement to group consent purposes.
• But this grouping concept does not mean anything to the consent manager.
• Proposed solution is to introduce properties for consent purposes, so that you can define groups or anything to that matter via properties.
• You are responsible for interpreting the properties.

[nirmal070125]

Should support searching from the property value as well