Model refactor: PaymentProcessor

[thekaveman]

Acceptance criteria

• Model renamed to TransitProcessor
• TransitAgency.payment_processor field renamed to TransitAgency.transit_processor
• All variable instances renamed to transit_processor
• All comments updated to remove mention of "payment"
• client_id moved to TransitAgency.transit_processor_client_id
• client_secret_name moved to TransitAgency.transit_processor_client_secret_name
• audience moved to TransitAgency.transit_processor_audience
• Each field in the model definition has a description
• Existing Django config data is migrated
• Docs are updated

Impact on the code

• Code search for audience in the repo
• Code search for client_id in the repo
• Code search for client_secret in the repo
• Code search for payment_processor in the repo
• Code search for PaymentProcessor in the repo

Impact on existing data

• Standard migrations for model/field renames should maintain existing data
• Data migration needed to move field data from old PaymentProcessor fields to new TransitAgency fields

Impact on analytics

• The card_tokenize_url and card_tokenize_func fields are logged in analytics, and are not changed in this scope other than to be on a differently named model
• EligibilityType.group_id is logged in analytics using the payment_group event property. Model refactor: PaymentProcessor Amplitude updates #2249 is a follow-up.

Impact on Admin permissions

• View permissions need to be updated for the new model name
• Edit permissions need to be updated for the new model name
• Field exclusions need to be updated to move the newly renamed/moved fields to the TransitAgencyAdmin