Added new sections to the Connection-Strings and Dependency-Injection documents.

docs/en/Connection-Strings.md

@@ -61,4 +61,13 @@ Once you want to separate a module's database, you typically will need to create
 
 ## Multi-Tenancy
 
-See [the multi-tenancy document](Multi-Tenancy.md) to learn how to use separate databases for tenants.
+See [the multi-tenancy document](Multi-Tenancy.md) to learn how to use separate databases for tenants.
+
+## Replace the Connection String Resolver
+
+ABP defines the `IConnectionStringResolver` and uses it whenever it needs a connection string. It has two pre-built implementations:
+
+* `DefaultConnectionStringResolver` uses the `AbpDbConnectionOptions` to select the connection string based on the rules defined in the "Configure the Connection Strings" section above.
+* `MultiTenantConnectionStringResolver` used for multi-tenant applications and tries to get the configured connection string for the current tenant if available. It uses the `ITenantStore` to find the connection strings. It inherits from the `DefaultConnectionStringResolver` and fallbacks to the base logic if no connection string specified for the current tenant.
+
+If you need a custom logic to determine the connection string, implement the `IConnectionStringResolver` interface (optionally derive from the existing implementations) and replace the existing implementation using the [dependency injection](Dependency-Injection.md) system.

docs/en/Dependency-Injection.md

@@ -166,6 +166,26 @@ public class BlogModule : AbpModule
 }
 ````
 
+### Replace a Service
+
+If you need to replace an existing service (defined by the ABP framework or another module dependency), you have two options;
+
+1. Use the `Dependency` attribute of the ABP framework as explained above.
+2. Use the `IServiceCollection.Replace` method of the Microsoft Dependency Injection library. Example:
+
+````csharp
+public class MyModule : AbpModule
+{
+    public override void ConfigureServices(ServiceConfigurationContext context)
+    {
+        //Replacing the IConnectionStringResolver service
+        context.Services.Replace(ServiceDescriptor.Transient<IConnectionStringResolver, MyConnectionStringResolver>());
+    }
+}
+````
+
+
+
 ## Injecting Dependencies
 
 There are three common ways of using a service that has already been registered.