Ovp-projects

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* Add max_applies to ProjectSearchSerializer
* Apply.status is now a delimited choice field.
* Apply.status returned by API is not an "key" field anymore, but a readable string, so instead of getting "applied" and "unapplied" you might now get "Applied" and "Canceled".
* Introduced route /projects/{project.slug}/applies/{apply.id}/ which can be PATCHED by the project owner, organization owner or organization member to modify the status of an apply by a valid key choice.
* Apply and unapply routes are changed:
/projects/{slug}/apply/ => /projects/{slug}/applies/apply/
/projects/{slug}/unapply/ => /projects/{slug}/applies/unapply/

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* Implement Project.hidden_address field.
* Fix Project.max_applies_from_roles updating when creating/removing VolunteerRole
* Add missing tests

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* Upgrade dependencies

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* Patch test_views.ApplyTestCase.test_unauthenticated_user_cant_apply_to_project to override settings

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* Add 'applied_count' to ProjectSearchSerializer
* Add 'minimum_age' field to Project model

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* Implement admin panel
* Use GoogleAddressLatLngSerializer instead of GoogleAddressSerializer on ProjectSearchSerializer
* Add 'max_applies' and 'public_project' to Project model
* Project 'image' is now nullable