Upgrade CI dependencies

- Update dotnet version
- Update dockerfile image versions

.github/workflows/ci.yml

@@ -23,7 +23,7 @@ jobs:
     - name: Install .NET Core
       uses: actions/setup-dotnet@v1
       with:
-        dotnet-version: '6.0.x'
+        dotnet-version: '7.0.x'
 
     - name: Build & test (Release)
       run: dotnet test src -c Release

Dockerfile

@@ -1,4 +1,4 @@
-FROM mcr.microsoft.com/dotnet/sdk:6.0.100 AS build
+FROM mcr.microsoft.com/dotnet/sdk:7.0 AS build
 WORKDIR /app
 
 RUN mkdir -p src/UnityNuGet && mkdir -p src/UnityNuGet.Server && mkdir -p src/UnityNuGet.Tests
@@ -13,7 +13,7 @@ COPY . ./
 RUN dotnet publish src -c Release -o /app/src/out
 
 # Build runtime image
-FROM mcr.microsoft.com/dotnet/aspnet:6.0
+FROM mcr.microsoft.com/dotnet/aspnet:7.0
 WORKDIR /app
 COPY --from=build /app/src/out .
 ENTRYPOINT ["dotnet", "UnityNuGet.Server.dll"]