CRM-20630: Modifying CRM_Activity_Form_Search to use URL parameters as search form values when passing force=1.

[coldrunKacper]

Overview

This is a simplified version of #10418 and does affect Activity Search Form only.

It allows to pass URL parameters as Search Form values when using with 'force=1' parameter.

It does not affect any other classes than CRM_Activity_Form_Search and does not modify $_defaults class property.

Before

Is not possible to do Activity search using URL parameters even if we use 'force=1' parameter.
For example, doing a GET request with following URLs does not work:

/civicrm/activity/search?force=1&activity_type_id[]=9&cid=3

/civicrm/activity/search?force=1&activity_type_id[]=9&activity_date_relative=earlier.year&activity_date_low=1&activity_date_high=1

Below we try to search for "Tell a Friend" activities (activity type id = 9) and for specified amount of time. As search results we Activities of all types and dates.
Results don't fit search values passed in URL:

Also search criteria are not set the URL values:

After

It's possible to pass search criteria with URL parameters.

Search results reflect URL parameters:

Fields of Search Form are set to values passed in URL:

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• CRM-20630: Find Activities: search criteria passing with URL parameters

[eileenmcnaughton]

Some combo of @totten / @colemanw / other commenters on original PR need to approve this

[MegaphoneJon]

It looks like this should be documented. @coldrunKacper are you able to submit a PR to the docs for this?