feat(share, config): more variables, placeholder and reset default (#132)

* More email share vars + unfinished placeolders config

{desc} {expires} vars
(unfinished) config placeholder vals

* done

* migrate

* edit seed

* removed comments

* refactor: replace dependecy `luxon` with `moment`

* update shareRecipientsMessage message

* chore: remove `luxon`

* fix: grammatically incorrect `shareRecipientsMessage` message

* changed to defaultValue and value instead

* fix: don't expose defaultValue to non admin user

* fix: update default value if default value changes

* refactor: set config value to null instead of a empty string

* refactor: merge two migrations into one

* fix value check empty

---------

Co-authored-by: Elias Schneider <login@eliasschneider.com>

backend/src/config/dto/adminConfig.dto.ts

@@ -8,6 +8,9 @@ export class AdminConfigDTO extends ConfigDTO {
   @Expose()
   secret: boolean;
 
+  @Expose()
+  defaultValue: string;
+
   @Expose()
   updatedAt: Date;