i want the ability to have contacts stored only locally on my phone (synced via carddav to my own server). then have a web api to attach one or multiple vcards

i want the ability to have contacts stored only locally on my phone (synced via carddav to my own server). then have a web api to attach one or multiple vcards (or specific fields from vcards). seems like a very sinple thing to spec out and implement. just press a button, pop up an address book, just like a file selector.