generate qr code svg (#2815)

* generate qr code svg prototype

* qr code for groups
fix formatting

* - letter avatar in qrcode
- escape xml in userinput (display/groupname)
- fix "Me" display name
- merge import declarations

* remove dot at the end of VerifyContactQRDescription

* if addr == displayname, show only one of them

Especially useful for yggmail accounts without usernames,
because the text would overflow otherwise.

* use real clipPath for rounded avatar

* - center avatar text better (dominant-baseline)
- add "sans-serif" to font fallback for text if arial is missing

* make corner always blue

* add [logo + "get.delta.chat"] footer to qrcode

* Update deltachat-ffi/deltachat.h

Co-authored-by: bjoern <r10s@b44t.com>

* Apply suggestions from code review

Co-authored-by: bjoern <r10s@b44t.com>

* new card design
- add stockstrings
- update changelog

* make qrcode pixels also #f2f2f2 instead of full white

* rename VERIFY_CONTACT_QR_DESC to SETUP_CONTACT
make footer text a tiny bit darker upon r10s's request

* avoid using  which is a doxygen command

* point out that one will join a group (this is still shorted and was also suggested in recent chats)

* add option to generate qr-code-svg to repl tool

* use same font-family in text and footer

* thinner card border

* remove superfluous <tspan> from footer to make color tweaking easier

* move font-weight to style, ios renderer does not pick it up from attribute; remove default font attributes not used consequently

* make get.delta.chat more visible

* align properly using dominant-baseline=central and alignment-baseline=middle, this makes things nice on all systems but android (before, ios was wrong and all others not 100% aligned as font metrics are ignored) (android needs a subsequent improvement)

Co-authored-by: bjoern <r10s@b44t.com>

deltachat-ffi/src/lib.rs

@@ -25,6 +25,7 @@ use std::time::{Duration, SystemTime};
 use anyhow::Context as _;
 use async_std::sync::RwLock;
 use async_std::task::{block_on, spawn};
+use deltachat::qr_code_generator::get_securejoin_qr_svg;
 use num_traits::{FromPrimitive, ToPrimitive};
 
 use deltachat::chat::{ChatId, ChatVisibility, MuteDuration, ProtectionStatus};
@@ -2075,6 +2076,27 @@ pub unsafe extern "C" fn dc_get_securejoin_qr(
         .strdup()
 }
 
+#[no_mangle]
+pub unsafe extern "C" fn dc_get_securejoin_qr_svg(
+    context: *mut dc_context_t,
+    chat_id: u32,
+) -> *mut libc::c_char {
+    if context.is_null() {
+        eprintln!("ignoring careless call to generate_verification_qr()");
+        return "".strdup();
+    }
+    let ctx = &*context;
+    let chat_id = if chat_id == 0 {
+        None
+    } else {
+        Some(ChatId::new(chat_id))
+    };
+
+    block_on(get_securejoin_qr_svg(ctx, chat_id))
+        .unwrap_or_else(|_| "".to_string())
+        .strdup()
+}
+
 #[no_mangle]
 pub unsafe extern "C" fn dc_join_securejoin(
     context: *mut dc_context_t,