gRPC: Implement endpoint 'getAccountInfo' (#2)

Added `getAccountInfo` to `Client` along with wrappers for all related generated types to keep it from being too unpleasant to work with.

Resolves https://concordium.atlassian.net/browse/CBW-1563.

Package.swift

@@ -6,8 +6,8 @@ let package = Package(
         name: "ConcordiumSwiftSDK",
         platforms: [
             // To be kept in sync with README.
-            .macOS(.v10_15),
             .iOS(.v15),
+            .macOS(.v10_15),
         ],
         products: [
             .library(

Sources/ConcordiumSwiftSDK/Client.swift

@@ -25,8 +25,16 @@ class Client {
         req.value = address.bytes
         let res = try await grpc.getNextAccountSequenceNumber(req).response.get()
         return NextAccountSequenceNumber(
-            sequenceNumber: res.sequenceNumber.value,
+            sequenceNumber: res.hasSequenceNumber ? res.sequenceNumber.value : nil,
             allFinal: res.allFinal
         )
     }
+
+    func getAccountInfo(of account: AccountIdentifier, at block: BlockIdentifier) async throws -> AccountInfo {
+        var req = Concordium_V2_AccountInfoRequest()
+        req.accountIdentifier = account.toGrpcType()
+        req.blockHash = block.toGrpcType()
+        let res = try await grpc.getAccountInfo(req).response.get()
+        return try .fromGrpcType(res)
+    }
 }