ENH: Implement queries and entity retrieval

Summary

See https://gitlab.indiscale.com/caosdb/customers/lfpb/management/-/issues/386.

Focus

Point the reviewer to the core of the code change. Where should they start
reading? What should they focus on (e.g. security, performance,
maintainability, user-friendliness, compliance with the specs, finding more
corner cases, concrete questions)?

Test Environment

How to set up a test environment for manual testing?

Check List for the Author

Please, prepare your MR for a review. Be sure to write a summary and a focus and create gitlab comments for the reviewer. They should guide the reviewer through the changes, explain your changes and also point out open questions. For further good practices have a look at our review guidelines

• All automated tests pass
• Reference related Issues
• Up-to-date CHANGELOG.md
• Annotations in code (Gitlab comments)
  • Intent of new code
  • Problems with old code
  • Why this implementation?

Check List for the Reviewer

• I understand the intent of this MR
• All automated tests pass
• Up-to-date CHANGELOG.md
• The test environment setup works and the intended behavior is reproducible in the test environment
• In-code documentation and comments are up-to-date.
• Check: Are there spezifications? Are they satisfied?

For further good practices have a look at our review guidelines.

src/Entity.jl

@@ -80,10 +80,10 @@ using CaosDB
 # and C++ only understand all-capital strings for datatypes,
 # importances, roles. What about user input like "record_type",
 # "RecordType", "recordtype"?
-""" 
+"""
 Struct containing a pointer to the wrapped cpp entity
 object. Meant for internal use; use `CaosDB.Entity.create_entity` to
-create an entity. 
+create an entity.
 """
 mutable struct _Entity
     wrapped_entity::Ptr{Cvoid}
@@ -111,10 +111,10 @@ mutable struct _Entity
 end
 
 
-""" 
+"""
 Struct containing a pointer to the wrapped cpp parent
 object. Meant for internal use; use `CaosDB.Entity.create_parent` to
-create an parent. 
+create an parent.
 """
 mutable struct _Parent
     wrapped_parent::Ptr{Cvoid}
@@ -142,10 +142,10 @@ mutable struct _Parent
 end
 
 
-""" 
+"""
 Struct containing a pointer to the wrapped cpp property
 object. Meant for internal use; use `CaosDB.Entity.create_property` to
-create an property. 
+create an property.
 """
 mutable struct _Property
     wrapped_property::Ptr{Cvoid}
@@ -254,12 +254,15 @@ end
     )
 
 Return a new entity object with role Record. If `name`, `datatype`, or
-`unit` were provided, its name, datatype, or unit are set accordingly.
+`unit` were provided, its name, datatype (including whether it is a
+reference or a list), or unit are set accordingly.
 """
 function create_property_entity(;
     name::AbstractString = "",
     datatype::AbstractString = "",
     unit::AbstractString = "",
+    is_reference::Bool = false,
+    is_list::Bool = false,
 )
 
     property = create_entity(name)
@@ -267,7 +270,7 @@ function create_property_entity(;
     set_role(property, "PROPERTY")
 
     if datatype != ""
-        set_datatype(property, datatype)
+        set_datatype(property, datatype, is_list = is_list, is_reference = is_reference)
     end
 
     if unit != ""
@@ -297,6 +300,9 @@ function create_property(;
     name::AbstractString = "",
     id::AbstractString = "",
     value::AbstractString = "",
+    datatype::AbstractString = "",
+    is_reference::Bool = false,
+    is_list::Bool = false,
 )
     property = Ref{_Property}(_Property(true))
 
@@ -317,6 +323,10 @@ function create_property(;
         set_id(property, id)
     end
 
+    if datatype != ""
+        set_datatype(property, datatype, is_reference = is_reference, is_list = is_list)
+    end
+
     if value != ""
         set_value(property, value)
     end
@@ -609,7 +619,7 @@ end
     function get_datatype(entity::Ref{_Entity})
 
 Return a tuple that contains the name of the datatype of the given
-`entity`, whether it is a reference, and whether it is a list. 
+`entity`, whether it is a reference, and whether it is a list.
 """
 function get_datatype(entity::Ref{_Entity})
 
@@ -1264,7 +1274,7 @@ to set the id of entities.
 function set_id(entity::Ref{_Entity}, id::AbstractString)
     throw(
         CaosDB.Exceptions.ClientException(
-            "You cannot set the id of an entity object.  
+            "You cannot set the id of an entity object.
 If you want to update an entity with this id, you have to retrieve it first.",
         ),
     )
@@ -1396,7 +1406,7 @@ end
 # too?
 """
     function set_datatype(
-        entity::Ref{_Entity}, 
+        entity::Ref{_Entity},
         datatype::AbstractString;
         is_list::Bool = false,
         is_reference::Bool = false,
@@ -1440,7 +1450,7 @@ end
 
 """
     function set_datatype(
-        property::Ref{_Property}, 
+        property::Ref{_Property},
         datatype::AbstractString;
         is_list::Bool = false,
         is_reference::Bool = false,