ENH: F remove value or property

Summary

Precondition for https://gitlab.indiscale.com/caosdb/customers/geomar/management/-/issues/110. Adds a function that removes a value from a property, and optionally, the property from the entity if it is empty afterwards. We used to implement this functionality in several customer-specific extensions, so I think it makes sense to have this upstream.

Focus

Check whether the behavior of the new function is reasonable also in the corner cases of list properties in which the value to be removed occurs more than once (i.e., remove "a" from ["a", "b", "a"]) and in case of an already empty property (remove "something" from None vs remove None from None).

Test Environment

Unit tests should be sufficient, but feel free to test it manually, too. Also check whether the docstring is understandable.

Check List for the Author

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• All automated tests pass
• Reference related issues
• Up-to-date CHANGELOG.md (or not necessary)
• Up-to-date JSON schema (or not necessary)
• Appropriate user and developer documentation (or not necessary)
  • How do I use the software? Assume "stupid" users.
  • How do I develop or debug the software? Assume novice developers.
• Annotations in code (Gitlab comments)
  • Intent of new code
  • Problems with old code
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Check List for the Reviewer

• I understand the intent of this MR
• All automated tests pass
• Up-to-date CHANGELOG.md (or not necessary)
• Appropriate user and developer documentation (or not necessary)
• The test environment setup works and the intended behavior is reproducible in the test environment
• In-code documentation and comments are up-to-date.
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For further good practices have a look at our review guidelines.

src/caosdb/common/models.py

 # -*- coding: utf-8 -*-
 #
-# ** header v3.0
 # This file is a part of the CaosDB Project.
 #
 # Copyright (C) 2018 Research Group Biomedical Physics,
 # Max-Planck-Institute for Dynamics and Self-Organization Göttingen
-# Copyright (C) 2020-2022 Indiscale GmbH <info@indiscale.com>
-# Copyright (C) 2020 Florian Spreckelsen <f.spreckelsen@indiscale.com>
+# Copyright (C) 2020-2023 Indiscale GmbH <info@indiscale.com>
+# Copyright (C) 2020-2023 Florian Spreckelsen <f.spreckelsen@indiscale.com>
 # Copyright (C) 2020-2022 Timm Fitschen <t.fitschen@indiscale.com>
 #
 # This program is free software: you can redistribute it and/or modify
@@ -22,7 +21,6 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program. If not, see <https://www.gnu.org/licenses/>.
 #
-# ** end header
 #
 
 """
@@ -47,6 +45,7 @@ from os import listdir
 from os.path import isdir
 from random import randint
 from tempfile import NamedTemporaryFile
+from typing import Any, Optional
 from warnings import warn
 
 from caosdb.common.datatype import (BOOLEAN, DATETIME, DOUBLE, INTEGER, TEXT,
@@ -453,6 +452,63 @@ class Entity:
 
         return self
 
+    def remove_value_from_property(self, property_name: str, value: Any,
+                                   remove_if_empty_afterwards: Optional[bool] = True):
+        """Remove a value from a property given by name.
+
+        Do nothing if this entity does not have a property of this
+        ``property_name`` or if the property value is different of the given
+        ``value``. By default, the property is removed form this entity if it is
+        empty (i.e., value=None) after removal of the value. This behavior can
+        be changed by setting ``remove_if_empty_afterwards`` to ``False`` in which
+        case the property remains.
+
+        Notes
+        -----
+        If the property value is a list and the value to be removed occurs more
+        than once in this list, only it's first occurrance is deleted (similar
+        to the behavior of Python's ``list.remove()``.)
+
+        If the property is already empty and a value != None is to be removed,
+        the property is not removed afterwards even if
+        ``remove_if_empty_afterwards`` is set to ``True`` (since it hasn't been
+        emptied **because** this function was called but rather didn't have a
+        value in the first place). This changes if the value to be removed is
+        set to ``None`` explicitly.
+
+        Parameters
+        ----------
+        property_name : str
+            Name of the property from which the ``value`` will be removed.
+        value
+            Value that is to be removed.
+        remove_if_empty_afterwards : bool, optional
+            Whether the property is to be removed from this entity if it is
+            emptied by removing the ``value``. Default is ``True``.
+
+        Returns
+        -------
+        self
+            This entity.
+        """
+
+        if self.get_property(property_name) is None:
+            return self
+        empty_afterwards = False
+        if isinstance(self.get_property(property_name).value, list):
+            if value in self.get_property(property_name).value:
+                self.get_property(property_name).value.remove(value)
+                if self.get_property(property_name).value == []:
+                    self.get_property(property_name).value = None
+                    empty_afterwards = True
+        elif self.get_property(property_name).value == value:
+            self.get_property(property_name).value = None
+            empty_afterwards = True
+        if remove_if_empty_afterwards and empty_afterwards:
+            self.remove_property(property_name)
+
+        return self
+
     def remove_parent(self, parent):
         self.parents.remove(parent)