Added an app concept to tye.yaml

- tye.yaml already has a name idea, when your applcation is split across multiple tye.yaml files, then the app groups them.
- The name field will be used to produce packages that encapsulate all services defined in a specific tye.yaml.

samples/multi-yaml/be/tye.yaml

@@ -1,4 +1,5 @@
-name: multi-tye
+app: multi-tye # name of the bigger application
+name: backend # name of this application
 services:
 - name: backend
   project: backend/backend.csproj

samples/multi-yaml/fe/tye.yaml

@@ -1,4 +1,5 @@
-name: multi-tye
+app: multi-tye # name of the bigger application
+name: frontend # name of this application
 services:
 - name: frontend
   project: frontend/frontend.csproj

src/Microsoft.Tye.Core/ApplicationBuilder.cs

@@ -13,12 +13,15 @@ namespace Microsoft.Tye
         {
             Source = source;
             Name = name;
+            Application = name;
         }
 
         public FileInfo Source { get; set; }
 
         public string Name { get; set; }
 
+        public string? Application { get; set; }
+
         public ContainerRegistry? Registry { get; set; }
 
         public List<ServiceBuilder> Services { get; } = new List<ServiceBuilder>();

src/Microsoft.Tye.Core/ApplicationFactory.cs

@@ -26,6 +26,7 @@ namespace Microsoft.Tye
             var rootConfig = ConfigFactory.FromFile(source);
             ValidateConfigApplication(rootConfig);
             var root = new ApplicationBuilder(source, rootConfig.Name ?? source.Directory.Name.ToLowerInvariant());
+            root.Application ??= rootConfig.Application;
 
             queue.Enqueue(rootConfig);
 

src/Microsoft.Tye.Core/ConfigModel/ConfigApplication.cs

@@ -21,6 +21,9 @@ namespace Microsoft.Tye.ConfigModel
 
         public string? Name { get; set; }
 
+        [YamlMember(Alias = "app")]
+        public string? Application { get; set; }
+
         public string? Registry { get; set; }
 
         public List<ConfigService> Services { get; set; } = new List<ConfigService>();