[Provider] Server entities and models (#1370)

* Mock out provider models and service

* Implement CreateAsync, CompleteSetupAsync, UpdateAsync, InviteUserAsync and ResendInvitesAsync

* Implement AcceptUserAsync and ConfirmUsersAsync

* Implement SaveUserAsync and DeleteUserAsync

* Add email templates

* Add admin operations for providers

* Fix mail template names

* Rename roles

* Verify provider has provideradmin

* Add self hosted check to admin controller

* Resolve review comments

* Update sql queries

* Change create provider to use email instead of userId

src/Sql/dbo/Stored Procedures/ProviderUser_DeleteByIds.sql

@@ -0,0 +1,42 @@
+CREATE PROCEDURE [dbo].[ProviderUser_DeleteByIds]
+    @Ids [dbo].[GuidIdArray] READONLY
+AS
+BEGIN
+    SET NOCOUNT ON
+
+    EXEC [dbo].[User_BumpAccountRevisionDateByProviderUserIds] @Ids
+
+    DECLARE @UserAndProviderIds [dbo].[TwoGuidIdArray]
+
+    INSERT INTO @UserAndProviderIds
+        (Id1, Id2)
+    SELECT
+        UserId,
+        ProviderId
+    FROM
+        [dbo].[ProviderUser] PU
+    INNER JOIN
+        @Ids PUIds ON PUIds.Id = PU.Id
+    WHERE
+        UserId IS NOT NULL AND
+        ProviderId IS NOT NULL
+
+    DECLARE @BatchSize INT = 100
+
+    -- Delete ProviderUsers
+    WHILE @BatchSize > 0
+        BEGIN
+        BEGIN TRANSACTION ProviderUser_DeleteMany_PUs
+
+        DELETE TOP(@BatchSize) OU
+        FROM
+            [dbo].[ProviderUser] PU
+        INNER JOIN
+            @Ids I ON I.Id = PU.Id
+
+        SET @BatchSize = @@ROWCOUNT
+
+        COMMIT TRANSACTION ProviderUser_DeleteMany_PUs
+    END
+END
+GO