Add support for Viewtype::Vcard

[adbenitez]

deltachat/deltachat-core-rust#5536 introduces a new viewtype Vcard (Viewtype::Vcard in JsonRPC, DC_MSG_VCARD in the C FFI). In order to show it, call the JsonRPC function parse_vcard(filePath) where filePath is the path to the message's attachment.

parse_vcard() will return a JSON struct with fields addr, display_name, profile_image, and color (which you can use to create a placeholder image in case there is no profile_image). You can ignore the other returned fields. Note that parse_vcard() returns a list of contacts; simply ignore all except for the first contact.

Android implements viewing Vcards here: deltachat/deltachat-android#3043

Can be done now (depends on deltachat/deltachat-core-rust#5536):

• display vcard messages in-chat
• display in quotes/replies
• display in draft/staging
• When a vCard is clicked, ask for confirmation and then call import_vcard() (depends on feat: Add import_vcard() (#5202) deltachat-core-rust#5582)

These TODO-items should be postponed:

• set new core stock string "Contact" (looks like we won't keep this stock string)

Preview from Android:

[nicodh]

@adbenitez what is meant with: set new core stock string "Contact" (used in summary)?

[iequidoo]

@adbenitez what is meant with: set new core stock string "Contact" (used in summary)?

Maybe we're going to remove this stock string at all as the contact name should be displayed instead of "Contact". And if a vCard can't be parsed, the message viewtype is changed to File anyway, so the file name is displayed instead.

EDIT: Currently this stock string is used, but with deltachat/deltachat-core-rust#5619 it isn't anymore.