[PM-17830] Backend changes for admin initiated sponsorships (#5531)

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* Add `Notes` column to `OrganizationSponsorships` table

* Add feature flag to `CreateAdminInitiatedSponsorshipHandler`

* Unit tests for `CreateSponsorshipHandler`

* More tests for `CreateSponsorshipHandler`

* Forgot to add `Notes` column to `OrganizationSponsorships` table in the migration script

* `CreateAdminInitiatedSponsorshipHandler` unit tests

* Fix `CreateSponsorshipCommandTests`

* Encrypt the notes field

* Wrong business logic checking for invalid permissions.

* Wrong business logic checking for invalid permissions.

* Remove design patterns

* duplicate definition in Constants.cs

* Allow rollback

* Fix stored procedures & type

* Fix stored procedures & type

* Properly encapsulating this PR behind its feature flag

* Removed comments

* Updated ValidateSponsorshipCommand to validate admin initiated requirements

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Co-authored-by: Conner Turnbull <133619638+cturnbull-bitwarden@users.noreply.github.com>
Co-authored-by: Conner Turnbull <cturnbull@bitwarden.com>

src/Core/AdminConsole/Entities/Organization.cs

@@ -114,6 +114,11 @@ public class Organization : ITableObject<Guid>, IStorableSubscriber, IRevisable,
     /// </summary>
     public bool UseRiskInsights { get; set; }
 
+    /// <summary>
+    /// If set to true, admins can initiate organization-issued sponsorships.
+    /// </summary>
+    public bool UseAdminSponsoredFamilies { get; set; }
+
     public void SetNewId()
     {
         if (Id == default(Guid))