Clear billing logic, do some cleanup

backend/spec/models.md

@@ -19,18 +19,13 @@ Activity is an audit log of all actions performed by a user or a worker process.
 - `created_at` - unix timestamp when the activity was created
 - `activity_type` is one of:
   - `create_tenant`
-  - `update_tenant_billing_anchor`
-  - `update_tenant_nwc_url`
+  - `update_tenant`
   - `create_relay`
   - `update_relay`
+  - `update_relay_plan`
   - `activate_relay`
   - `deactivate_relay`
   - `fail_relay_sync`
-  - `create_invoice`
-  - `mark_invoice_paid`
-  - `mark_invoice_attempted`
-  - `mark_invoice_sent`
-  - `mark_invoice_closed`
 - `resource_type` is a string identifying the resource type being modified.
 - `resource_id` is a string identifying the resource id being modified.
 
@@ -58,7 +53,6 @@ Tenants are customers of the service, identified by a nostr `pubkey`. Public met
 - `pubkey` is the nostr public key identifying the tenant
 - `nwc_url` (private) a nostr wallet connect URL used for **paying** invoices generated by the system
 - `created_at` unix timestamp identifying tenant creation time
-- `billing_anchor` unix timestamp identifying billing cycle anchor. This gets reset when the tenant has no paid relays and adds (or reactivates) one.
 
 # Relay
 
@@ -69,7 +63,8 @@ A relay is a nostr relay owned by a `tenant` and hosted by the attached zooid in
 - `schema` - the relay's db schema (read_only, calculated based on `subdomain` + `id`)
 - `subdomain` - the relay's subdomain
 - `plan` - the relay's plan
-- `status` - `new|active|inactive`. Only `active` relays count toward billing.
+- `status` - `active|inactive`. Only `active` relays count toward billing.
+- `synced` - whether the relay has been successfully synced to zooid at least once.
 - `sync_error` - a string indicating any errors encountered when synchronizing.
 - `info_name` - the relay's name
 - `info_icon` - the relay's icon image URL
@@ -81,7 +76,6 @@ A relay is a nostr relay owned by a `tenant` and hosted by the attached zooid in
 - `blossom_enabled` - whether blossom file storage is enabled
 - `livekit_enabled` - whether livekit calls are enabled
 - `push_enabled` - whether relay push is enabled
-- `synced` (private) - whether the relay has been successfully synced to zooid at least once. Used by infra to decide POST vs PUT.
 
 Some attributes persisted to zooid via API have special handling:
 
@@ -91,29 +85,3 @@ Some attributes persisted to zooid via API have special handling:
 - The relay's `livekit_*` configuration is inferred based on environment variables and `livekit_enabled`.
 - The relay's `roles` are hard-coded for now.
 
-# Invoice
-
-Invoices are generated at the end of a tenant's monthly billing period. The billing module is responsible for creating them, collecting them, and dunning them.
-
-- `id` - random invoice ID
-- `tenant` - tenant pubkey
-- `status` - `pending|paid|closed`
-- `amount` is derived as the sum of associated invoice item `sats` values (not stored as a separate source of truth)
-- `created_at` - unix timestamp for when the invoice was created
-- `attempted_at` - nullable unix timestamp for when collection was last attempted
-- `error` - optional human-readable error from the last failed collection attempt
-- `closed_at` - nullable unix timestamp for when the invoice was closed
-- `sent_at` - nullable unix timestamp for when the invoice was sent via DM
-- `paid_at` - nullable unix timestamp for when the invoice was paid
-- `bolt11` - a BOLT 11 lightning invoice that can be used to pay the invoice
-- `period_start` - unix timestamp for period start
-- `period_end` - unix timestamp for period end
-
-# Invoice Item
-
-Invoice items are attached to an invoice and represent charges for a given relay.
-
-- `id` - random invoice item ID
-- `invoice` - invoice ID
-- `relay` - relay ID
-- `sats` - amount in satoshis