Copy file to received shared file

Steps to reproduce

1. Alice creates a file "test.txt" with content "original text"
2. Alice shares the file with Brian
3. Brian creates a file "new.txt" with content "new text"
4. Brian copies "new.txt" to "test.txt"

Expected behaviour

Both Alice and Brian see that "test.txt" has the content "new text"

Actual behaviour

Brian now has "test.txt" has the content "new text"
The share from Alice to Brian is in the declined state
Alice has "test.txt" has the content "original text"

When Brian accepts the declined share from Alice, then Brian sees "test (2).txt" with content "original text"

Server configuration

Current oC10 core master

See PR #40308 for the test scenario(s)