Refactor App Config tsp (Azure#32338)

* add aliases and fix casing

* update alias casing

* refactor shared code

* create alias for shared request params

* clean up implementation

* merge more request params

* format

* update alias

---------

Co-authored-by: catalinaperalta <caperal@microsoft.com>

Author: catalinaperalta

specification/appconfiguration/AppConfiguration/models.tsp

@@ -328,3 +328,116 @@ model OperationDetails {
     """)
   error?: Foundations.Error;
 }
+
+alias SyncTokenHeader = {
+  @doc("Used to guarantee real-time consistency between requests.")
+  @header("Sync-Token")
+  syncToken?: string;
+};
+
+#suppress "@azure-tools/typespec-azure-core/no-closed-literal-union" "Needs fix: https://github.com/microsoft/typespec/issues/2853"
+alias ContentTypeHeader<T extends string> = {
+  @doc("Content-Type header")
+  @header("Content-Type")
+  contentType?: T | "application/problem+json";
+};
+
+alias AppConfigResponseHeaders = {
+  ...SyncTokenHeader;
+
+  @doc("A value representing the current state of the resource.")
+  @header("ETag")
+  etagHeader?: string;
+};
+
+alias AfterHeader = {
+  @doc("""
+    Instructs the server to return elements that appear after the element referred
+    to by the specified token.
+    """)
+  @query("After")
+  after?: string;
+};
+
+alias AcceptDatetimeHeader = {
+  @doc("""
+    Requests the server to respond with the state of the resource at the specified
+    time.
+    """)
+  @header("Accept-Datetime")
+  acceptDatetime?: string;
+};
+
+alias SelectQueryParam<Type extends TypeSpec.Reflection.Model | string> = {
+  @doc("Used to select what fields are present in the returned resource(s).")
+  @query("$Select")
+  select?: Type[];
+};
+
+alias NameQueryParam<TDoc extends valueof string> = {
+  @doc(TDoc)
+  @query("name")
+  name?: string;
+};
+
+alias KeyQueryParam<TDoc extends valueof string> = {
+  @doc(TDoc)
+  @query("key")
+  key?: string;
+};
+
+alias IfMatchHeader = {
+  @doc("""
+    Used to perform an operation only if the targeted resource's etag matches the
+    value provided.
+    """)
+  @header("If-Match")
+  ifMatch?: string;
+};
+
+alias IfNoneMatchHeader = {
+  @doc("""
+    Used to perform an operation only if the targeted resource's etag does not
+    match the value provided.
+    """)
+  @header("If-None-Match")
+  ifNoneMatch?: string;
+};
+
+alias KeyPathParam<TDoc extends valueof string> = {
+  @doc(TDoc)
+  @path
+  key: string;
+};
+
+alias LabelQueryParam<TDoc extends valueof string> = {
+  @doc(TDoc)
+  @query("label")
+  label?: string;
+};
+
+alias SnapshotOptionalQueryParam<TDoc extends valueof string> = {
+  @doc(TDoc)
+  @query("snapshot")
+  snapshot?: string;
+};
+
+alias TagsQueryParam<TDoc extends valueof string> = {
+  #suppress "@azure-tools/typespec-azure-core/no-query-explode" "Pre-existing API contract."
+  @doc(TDoc)
+  @query(#{ name: "tags", explode: true })
+  tags?: string[];
+};
+
+alias LinkHeader = {
+  @doc("Includes links to related resources.")
+  @header("Link")
+  link?: string;
+};
+
+alias NamePathParam<TDoc extends valueof string> = {
+  @doc(TDoc)
+  @maxLength(256)
+  @path
+  name: string;
+};