### Steps to reproduce

Begin of the insertion**Common steps:**

End of the insertion 1. Be a non admin user

2. Have two projects

1. "Project read only": The user is member in here but does not have the "Manage work package relations" permission

2. "Project writable": The user is member with the permission "Manage work package relations" permission

3. Have two work packages one in each project

1. "Work package read only"

2. "Work package writable"

4. Go to the writable ticket "Work package writable" Begin of the insertion


**Create case:**

1.End of the insertion Begin of the deletion

5.End of the deletion Go to the relations tab and open the modal to create a new "Blocks" permission (Also possible for other relations)

Begin of the insertion2.End of the insertion Begin of the deletion 6.End of the deletion Insert "Work package read only"

Begin of the insertion3.End of the insertion Begin of the deletion 7.End of the deletion Click "Add"


Begin of the insertion**Update case (If there already is an existing relation):**

1. Go to the relations tab and click on the three dots menu for the relation to the read only WP

2. Click "Edit relation"

3. Update the description

4. Click "Save"


**Delete case (If there already is an existing relation):**

1. Go to the relations tab and click on the three dots menu for the relation to the read only WP

2. Click "Delete relation"


End of the insertion ### What is the buggy behavior?

Begin of the insertion**Create case:**

End of the insertion * The relation is created.


Begin of the insertion**Update case (If there already is an existing relation):**

* The relation is updated.


**Delete case (If there already is an existing relation):**

* The relation is deleted.


End of the insertion ### What is the expected behavior?

Begin of the insertion**Common:**

End of the insertion * We Begin of the insertionenforceEnd of the insertion Begin of the deletion enforeEnd of the deletion symmetry; the user needs write permission on both work packages in order to be able to create the relation. Begin of the insertion


**Create case:**

End of the insertion Begin of the deletion

End of the deletion * Relations with read-only permissions are still visible in the results. However, selecting one Begin of the insertionthrowsEnd of the insertion Begin of the deletion throwEnd of the deletion an in-line error below the field with text:

* "The selected work package is read-only and cannot be added as a relation."


Begin of the insertion**Update case (If there already is an existing relation):**

* "This relation cannot be updated because the related work package is read-only."


**Delete case (If there already is an existing relation):**

* "This relation cannot be deleted because the related work package is read-only."

<br>


End of the insertion ### Screenshots and other files

<img class="op-uc-image op-uc-image_inline" src="/api/v3/attachments/314824/content">

### Technical notes

This is possible because the `relations/base_contract.rb` only checks the `model.from` work package for the permission.