Completion Suggestion view for user mentions (#1859)

* created the list but I need to find a way to overlay it

* make the list able to have an intrinsic height

* best solution so far but does not work with expansion

* needs testing

* more scalable solution

* tests completed

* changelog

* injecting the media provider

* fix tests

* pr suggestions

* better testing

UnitTests/Sources/CompletionSuggestionServiceTests.swift

@@ -0,0 +1,53 @@
+//
+// Copyright 2023 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import Combine
+import XCTest
+
+@testable import ElementX
+
+final class CompletionSuggestionServiceTests: XCTestCase {
+    private var cancellables = Set<AnyCancellable>()
+    
+    override func setUp() {
+        cancellables.removeAll()
+    }
+    
+    func testUserSuggestons() async throws {
+        let alice: RoomMemberProxyMock = .mockAlice
+        let members: [RoomMemberProxyMock] = [alice, .mockBob, .mockCharlie, .mockMe]
+        let roomProxyMock = RoomProxyMock(with: .init(displayName: "test", members: members))
+        let service = CompletionSuggestionService(roomProxy: roomProxyMock, areSuggestionsEnabled: true)
+        
+        var deferred = deferFulfillment(service.suggestionsPublisher) { suggestions in
+            suggestions == []
+        }
+        
+        try await deferred.fulfill()
+        
+        deferred = deferFulfillment(service.suggestionsPublisher) { suggestions in
+            suggestions == [.user(item: .init(id: alice.userID, displayName: alice.displayName, avatarURL: alice.avatarURL))]
+        }
+        service.setSuggestionTrigger(.init(type: .user, text: "ali"))
+        try await deferred.fulfill()
+        
+        deferred = deferFulfillment(service.suggestionsPublisher) { suggestions in
+            suggestions == []
+        }
+        service.setSuggestionTrigger(.init(type: .user, text: "me"))
+        try await deferred.fulfill()
+    }
+}