feat(api): Add is_bot to cffi and jsonrpc (#5197)

@adbenitez wants this feature on Deltalab to display a bot tag. 
Other UIs might also want to adopt this feature :)

---------
Co-authored-by: link2xt <link2xt@testrun.org>

deltachat-ffi/deltachat.h

@@ -5072,6 +5072,15 @@ int             dc_contact_is_blocked        (const dc_contact_t* contact);
  */
 int             dc_contact_is_verified       (dc_contact_t* contact);
 
+/**
+ * Returns whether contact is a bot.
+ *
+ * @memberof dc_contact_t
+ * @param contact The contact object.
+ * @return 0 if the contact is not a bot, 1 otherwise.
+ */
+int             dc_contact_is_bot            (dc_contact_t* contact);
+
 
 /**
  * Return the contact ID that verified a contact.

deltachat-ffi/src/lib.rs

@@ -4132,6 +4132,15 @@ pub unsafe extern "C" fn dc_contact_is_verified(contact: *mut dc_contact_t) -> l
     }
 }
 
+#[no_mangle]
+pub unsafe extern "C" fn dc_contact_is_bot(contact: *mut dc_contact_t) -> libc::c_int {
+    if contact.is_null() {
+        eprintln!("ignoring careless call to dc_contact_is_bot()");
+        return 0;
+    }
+    (*contact).contact.is_bot() as libc::c_int
+}
+
 #[no_mangle]
 pub unsafe extern "C" fn dc_contact_get_verifier_id(contact: *mut dc_contact_t) -> u32 {
     if contact.is_null() {

deltachat-jsonrpc/src/api/types/contact.rs

@@ -45,6 +45,9 @@ pub struct ContactObject {
     /// the contact's last seen timestamp
     last_seen: i64,
     was_seen_recently: bool,
+
+    /// If the contact is a bot.
+    is_bot: bool,
 }
 
 impl ContactObject {
@@ -80,6 +83,7 @@ impl ContactObject {
             verifier_id,
             last_seen: contact.last_seen(),
             was_seen_recently: contact.was_seen_recently(),
+            is_bot: contact.is_bot(),
         })
     }
 }