Add a public modifier to an interface method
merged branch elnur/interface-public-modifier (PR #7397)

This PR was submitted for the 2.0 branch but it was merged into the 2.1 branch instead (closes #7397).

Commits
-------

8ee05e5 Add a public modifier to an interface method

Discussion
----------

[2.0][Security] Add a public modifier to an interface method

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes