all: Aggiunte varie feature e riscritte svariate cose

shared/model.ts

@@ -2,7 +2,7 @@
 // Common
 //
 
-export type MetadataProps = 'id' | 'createdAt'
+export type MetadataProps = 'id' | 'createdAt' | 'deleted'
 
 export type Opaque<T, K, L extends string = 'opaque'> = T & { _: K; __: L }
 export type Id<T> = Opaque<string, T, 'id'>
@@ -41,7 +41,9 @@ export type ProblemId = Id<Problem>
 export type Problem = {
     id: ProblemId
     createdAt: string
+    deleted: boolean
 
+    title: string
     content: string
     createdBy: UserId
 }
@@ -57,6 +59,7 @@ export type SolutionId = Id<Solution>
 export type Solution = {
     id: SolutionId
     createdAt: string
+    deleted: boolean
 
     sentBy: UserId
     forProblem: ProblemId