Move collections to abstractions

src/Umbraco.Core/Collections/CompositeStringStringKey.cs

@@ -1,41 +0,0 @@
-using System;
-
-namespace Umbraco.Core.Collections
-{
-    /// <summary>
-    /// Represents a composite key of (string, string) for fast dictionaries.
-    /// </summary>
-    /// <remarks>
-    /// <para>The string parts of the key are case-insensitive.</para>
-    /// <para>Null is NOT a valid value for neither parts.</para>
-    /// </remarks>
-    public struct CompositeStringStringKey : IEquatable<CompositeStringStringKey>
-    {
-        private readonly string _key1;
-        private readonly string _key2;
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="CompositeStringStringKey"/> struct.
-        /// </summary>
-        public CompositeStringStringKey(string key1, string key2)
-        {
-            _key1 = key1?.ToLowerInvariant() ?? throw new ArgumentNullException(nameof(key1));
-            _key2 = key2?.ToLowerInvariant() ?? throw new ArgumentNullException(nameof(key2));
-        }
-
-        public bool Equals(CompositeStringStringKey other)
-            => _key2 == other._key2 && _key1 == other._key1;
-
-        public override bool Equals(object obj)
-            => obj is CompositeStringStringKey other && _key2 == other._key2 && _key1 == other._key1;
-
-        public override int GetHashCode()
-            => _key2.GetHashCode() * 31 + _key1.GetHashCode();
-
-        public static bool operator ==(CompositeStringStringKey key1, CompositeStringStringKey key2)
-            => key1._key2 == key2._key2 && key1._key1 == key2._key1;
-
-        public static bool operator !=(CompositeStringStringKey key1, CompositeStringStringKey key2)
-            => key1._key2 != key2._key2 || key1._key1 != key2._key1;
-    }
-}