Add Npgsql and ConnectionString

Helios/Helios.csproj

@@ -8,8 +8,12 @@
 
   <ItemGroup>
     <None Remove="Source\" />
+    <None Remove="Npgsql" />
   </ItemGroup>
   <ItemGroup>
     <Folder Include="Source\" />
   </ItemGroup>
+  <ItemGroup>
+    <PackageReference Include="Npgsql" Version="6.0.4" />
+  </ItemGroup>
 </Project>

Helios/appsettings.json

 {
+  "ConnectionStrings": {
+    "Default": "User ID=myusername;Password=mypassword;Host=localhost;Port=5432;Database=helios;Pooling=true;Min Pool Size=0;Max Pool Size=100;Connection Lifetime=0;"
+  },
   "Logging": {
     "LogLevel": {
       "Default": "Information",