[FEA]Create DICOM Encapsulated PDF object with provided bytes of a PDF file

[MMelQin]

Is your feature request related to a problem? Please describe.
There is a need to encapsulate a PDF of already generated or scanned report in DICOM Encapsulated PDF object. A writer in App SDK will help users to accelerate app implementation even if the writer simply takes care of generating the DICOM object with PDF bytes.
Describe the solution you'd like
A built-in operator to take in bytes of the PDF, optionally the metadata of a study for its study instance UID, and to save DICOM Encapsulated PDF instance file.
Describe alternatives you've considered
It would be nice to support formatting and converting text or even images into structured PDF content before writing the DICOM object, though it is understood that there could be many user specific templates, ways of associating and arranging text and images, and embedding the logic in the writer may not be feasible and hard for users to customize.
Additional context
The existing Basic Text SR Writer has functions to write DICOM common modules, SOP common, Patient, Study, etc, and can be reused.