This commit introduces support for AccountMigration federation message
receive. It covers the cases when the new home pod for a user is remote
respective to the recepient pod of the message. It also allows to initiate
migration locally by a podmin from the rails console. This will give the
pods a possibility to understand the account migration event on the
federation level and thus future version which will implement migration
will be backward compatible with the pods starting from this commit.

This commit introduces changes to the user data export archive format.
This extends data set which is included in the archive. This data can be
then imported to other pods when this feature is implemented.

Also the commit adds the archive format json schema. ATM it is used in
automatic tests only, but in future it will also be used to validate
incoming archives.

This commit refactors account deletion spec by moving data creation to a helper
object DataGenerator.

ClientsController and TokenEndpointController are called from the outside,
so CSRF verification prevents them from normal operation.

closes #7062

closes #7043

message doesn't include Diaspora::Relayable anymore

* add port to pods
* remove url from person and link people with pod-table

See

- http://openid.net/specs/openid-connect-core-1_0.html#ClientAuthentication
- https://openid.net/specs/openid-connect-registration-1_0.html#ClientMetadata

- Add foreign_keys
- Remove unused classes/methods
- Fix pronto errors
- Add method to retrieve client id from name
- Remove TODO comments
- Fix unnecessary private key generation

- fix map controls in stream

- add coordinates in post_presenter
- add map to the SPV if location is provided
- add leaflet.js to render map and marker of position
- make coordinates available in frontend
- add map scss
- make stream post location clickable and redirect to the SPV
- prevent render map if no location data is provided
- add tests for coordinates
- use the leaflet gem instead of the JS assets
(#5813)

add tooltips in the frontend
fix a JS problem with empty hostname
use `find_in_batches` correctly
add a migration to clean up the pods table + unique index on hostname

* add a class for checking pod connectivity
* extend pod model to handle new functionality
* add an admin frontend to list pods and re-trigger checks manually
* add a daily worker to run through all the pods
* add unit tests for most of the new code

closes #6007

For example if they're already present
Also refactor StatusMessage XML specs