Syntax:
ActionPlansUtilitiesExternal.ApplyActionPlan(
    @newActionPlanName,     
    @templateId,     
    @recordId,     
    @objectApiName
);
 
Parameters:
@newActionPlanName
The name of the newly created Activity Plan.

@templateId 
The record ID of the Activity Plan Template to be used for the new Activity Plan.

@recordId
The record ID of the source object the new Activity Plan is being created for. This will be either a Matter, Account or Contact ID as specified in the next parameter.

@objectApiName
The API name of the base object for the ID specified in the record ID.
Options are 'advpm__Matter__c' for Matter, 'Account' for Account and 'Contact' for Contact.

Result:
The function call will return a JSON formatted string in this format: {success:"",result:""} 

success
Will be either TRUE or FALSE

result
Confirmation message of process completion OR Error message if process is hauled with any unexpected error.  

Example:
ActionPlansUtilitiesExternal.ApplyActionPlan(
    'My New ActionPlan',  
    'a0A9000000RJhKTEA1',  
    'a05900000051CpN',  
    'advpm__Matter__c'
);

Note:
Multiple recordId parameters can be passed to create a multiple new Activity Plans for several Matter objects with a single function call. Use a ',' (comma) to separate the ID values. e.g: 'a05900000051CpN,a05900000052CpN,a05900000053CpN'  

Example Using a Button from the Matter Context