Introduce backend and frontend support for generating Stripe payment
links
for outstanding booking balances. Adds a new POST endpoint to create
payment
links, updates booking view to include a Stripe button, and integrates
error handling and feedback for payment link creation. Refactors view
models and templates to support the new feature.
Eliminated all references to the Stripe Connect account configuration
and
option handling. This includes removing the related environment
variable,
config struct field, client option, and usage in Stripe client setup.
Stripe integration now only uses the main secret key and webhook secret.
