Solution refers to projects outside of this repo

It is not possible to open this solution when pulling this, because there are two project in it which are not included. 

```
    <ProjectReference Include="..\..\..\LTI\LtiAdvantage\src\LtiAdvantage.IdentityServer4\LtiAdvantage.IdentityServer4.csproj" />
    <ProjectReference Include="..\..\..\LTI\LtiAdvantage\src\LtiAdvantage\LtiAdvantage.csproj" />

```