[optim] Download 30 added items at once in a single HTTP request from the server

Cargo.lock

@@ -113,6 +113,12 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "either"
+version = "1.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e78d4f1cc4ae33bbfc157ed5d5a5ef3bc29227303d595861deb238fcec4e9457"
+
 [[package]]
 name = "encoding_rs"
 version = "0.8.29"
@@ -381,6 +387,15 @@ version = "2.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "68f2d64f2edebec4ce84ad108148e67e1064789bee435edc5b60ad398714a3a9"
 
+[[package]]
+name = "itertools"
+version = "0.10.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a9a9d19fa1e79b6215ff29b9d6880b706147f16e9b1dbb1e4e5947b5b02bc5e3"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "itoa"
 version = "0.4.8"
@@ -407,6 +422,7 @@ dependencies = [
  "env_logger",
  "ical-daladim",
  "ics",
+ "itertools",
  "log",
  "minidom",
  "once_cell",