remove the oboslete marker

It caused problems when using inheritance

Server/Server/Models/City.cs

@@ -24,9 +24,7 @@ namespace Server.Models
         [DataMember]
         public virtual Country Country { get => _Counry; set => _Counry = value; }
 
-        [Obsolete("Only needed for serialization and materialization", true)]
         public City() { }
-
         public City (string name, int zipCode, Country country)
         {
             this.Name = name;

Server/Server/Models/Doctor.cs

@@ -21,7 +21,6 @@ namespace Server.Models
         [DataMember]
         public virtual Status Status { get => _Status; set => _Status = value; }
 
-        [Obsolete("Only needed for serialization and materialization", true)]
         public Doctor() { }
         public Doctor (Person person, Status status)
         {

Server/Server/Models/Exam.cs

@@ -27,7 +27,6 @@ namespace Server.Models
         [DataMember]
         public virtual Result Result { get => _Result; set => _Result = value; }
 
-        [Obsolete("Only needed for serialization and materialization", true)]
         public Exam() { }
         public Exam (Doctor doctor, Person patient, Result result)
         {

Server/Server/Models/Gender.cs

@@ -18,7 +18,6 @@ namespace Server.Models
         [DataMember]
         public string Name { get => _Name; set => _Name = value; }
 
-        [Obsolete("Only needed for serialization and materialization", true)]
         public Gender() { }
         public Gender (string name)
         {

Server/Server/Models/Person.cs

@@ -33,7 +33,6 @@ namespace Server.Models
         [DataMember]
         public virtual City City { get => _City; set => _City = value; }
 
-        [Obsolete("Only needed for serialization and materialization", true)]
         public Person() { }
         public Person (string firstName, string lastName, Gender gender, Salutation salutation,
                        string streetName, City city)

Server/Server/Models/Result.cs

@@ -27,7 +27,6 @@ namespace Server.Models
         [DataMember]
         public bool Infected { get => _Infected; set => _Infected = value; }
 
-        [Obsolete("Only needed for serialization and materialization", true)]
         public Result() { }
         public Result (string name, string description, Strain strain, bool infected)
         {

Server/Server/Models/Salutation.cs

@@ -18,7 +18,6 @@ namespace Server.Models
         [DataMember]
         public string Name { get => _Name; set => _Name = value; }
 
-        [Obsolete("Only needed for serialization and materialization", true)]
         public Salutation() { }
         public Salutation (string name)
         {

Server/Server/Models/Status.cs

@@ -18,7 +18,6 @@ namespace Server.Models
         [DataMember]
         public string Name { get => _Name; set => _Name = value; }
 
-        [Obsolete("Only needed for serialization and materialization", true)]
         public Status() { }
         public Status (string name)
         {

Server/Server/Models/Strain.cs

@@ -18,7 +18,6 @@ namespace Server.Models
         [DataMember]
         public string Name { get => _Name; set => _Name = value; }
 
-        [Obsolete("Only needed for serialization and materialization", true)]
         public Strain() { }
         public Strain (string name)
         {