Test variable evaluation via cqf expressions

[ageryck]

Describe the feature request.
Allow the SDC to evaluate variables passed with definite values to be evaluated via cqf expression. An example will be testing a minDate value of a static date provided to validate the datepicker widget.

Additional context
Refer to these two tickets
google/android-fhir#2292
google/android-fhir#1759

And the Implementing PR - google/android-fhir#2326

Acceptance criteria

• Ability to set a minDate on the date picker and use it for widget validation
• Ability to use a static date such as patient dob as a minDate
• Documentation on feature use

Implementation plan (For Engineers)
The plan for implementing the solution e.g. via a description or a check list for the various ordered tasks that will need to be completed.
_i.e. Describe how you intend to solve the problem

Demo

Image of when date min value is today - 6 days and max date is today	Image of when min date is birthdate and max date is today	Image of when max date is today five days beyond

[brandyodhiambo]

@ndegwamartin and @ageryck have tested the first two cases when the minimum date is set to the patient's birthdate and when it is set to a given date. the date picker restricts dates to be picked according to the values respectively you can see the images appended above.

[ageryck]

@brandy-kay the first screenshot looks okay however it is not visible on the second kindly confirm it is restricted based on the patient birthdate queried through an expression and equally limits the max value as set. If yes then you can proceed to add some documentation about this.

[brandyodhiambo]

sure @ageryck let me test it futher