Implements credential storage in the lib.

Cargo.lock

@@ -1964,6 +1964,16 @@ dependencies = [
  "unicode-segmentation",
 ]
 
+[[package]]
+name = "keyring"
+version = "3.6.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eebcc3aff044e5944a8fbaf69eb277d11986064cba30c468730e8b9909fb551c"
+dependencies = [
+ "log",
+ "zeroize",
+]
+
 [[package]]
 name = "libappindicator"
 version = "0.9.0"
@@ -2175,7 +2185,10 @@ name = "nextcloud_client"
 version = "0.1.0"
 dependencies = [
  "bytes",
+ "dirs",
  "futures-util",
+ "keyring",
+ "open",
  "pin-project-lite",
  "reqwest 0.12.28",
  "serde",