[FEAT]: street_network backend configuration by user

[kadhikari]

Street network backends are stored in the table streetnetwork_backend.
They are used in the following attributes of the table instance:

• street_network_bss
• street_network_ridesharing
• street_network_taxi
• street_network_car_no_park
• street_network_car
• street_network_walking
• street_network_bike
  So a street_network backend is configured for an instance (coverage) + mode.

This feature will allow to configure a street_network backend for a user + mode.

• To have minimum time delay while fetching street_network backend for a user + mode, an attribute has_sn_backend is used.
• The new table sn_backend_authorization is excluded from automatic join while getting user for each request to navitia.
• Attribute user.has_sn_backend is manipulated by /post and /delete on api /sn_backend_authorizations
• In the api /users, sn_backend_authorizations will be present.

For more details: https://navitia.atlassian.net/browse/NAV-2800

[sonarqubecloud]

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