v2 RC2 (#33)

* Add PostgreSQL back end (#30)
* Upgrade password storage (#32)
* Change podcast/episode storage for SQLite (#29)
* Move date/time handling to NodaTime (#31)

src/MyWebLog.Data/Interfaces.fs

@@ -1,9 +1,10 @@
 namespace MyWebLog.Data
 
-open System
 open System.Threading.Tasks
 open MyWebLog
 open MyWebLog.ViewModels
+open Newtonsoft.Json
+open NodaTime
 
 /// The result of a category deletion attempt
 type CategoryDeleteResult =
@@ -137,7 +138,7 @@ type IPostData =
         WebLogId -> tag : string -> pageNbr : int -> postsPerPage : int -> Task<Post list>
     
     /// Find the next older and newer post for the given published date/time (excluding revisions and prior permalinks)
-    abstract member FindSurroundingPosts : WebLogId -> publishedOn : DateTime -> Task<Post option * Post option>
+    abstract member FindSurroundingPosts : WebLogId -> publishedOn : Instant -> Task<Post option * Post option>
     
     /// Restore posts from a backup
     abstract member Restore : Post list -> Task<unit>
@@ -326,6 +327,9 @@ type IData =
     /// Web log user data functions
     abstract member WebLogUser : IWebLogUserData
     
+    /// A JSON serializer for use in persistence
+    abstract member Serializer : JsonSerializer
+    
     /// Do any required start up data checks
     abstract member StartUp : unit -> Task<unit>