Enable TreatWarningsAsErrors for more projects

Jellyfin.Api/Jellyfin.Api.csproj

@@ -9,6 +9,7 @@
     <TargetFramework>netstandard2.1</TargetFramework>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>

Jellyfin.Api/Models/StartupDtos/StartupConfigurationDto.cs

@@ -1,3 +1,5 @@
+#nullable disable
+
 namespace Jellyfin.Api.Models.StartupDtos
 {
     /// <summary>

Jellyfin.Api/Models/StartupDtos/StartupUserDto.cs

@@ -1,3 +1,5 @@
+#nullable disable
+
 namespace Jellyfin.Api.Models.StartupDtos
 {
     /// <summary>

Jellyfin.Data/Jellyfin.Data.csproj

@@ -4,6 +4,7 @@
     <TargetFrameworks>netstandard2.0;netstandard2.1</TargetFrameworks>
     <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
+    <TreatWarningsAsErrors Condition=" '$(Configuration)' == 'Release' ">true</TreatWarningsAsErrors>
   </PropertyGroup>
 
   <PropertyGroup Condition=" '$(Configuration)' == 'Debug' ">

RSSDP/RSSDP.csproj

@@ -14,6 +14,7 @@
   <PropertyGroup>
     <TargetFramework>netstandard2.1</TargetFramework>
     <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
   </PropertyGroup>
 
 </Project>