[AHMv2] Move Para Registrar functionality from RC to CT

[Ank4n]

Existing Apis:

Call index	Call name	Origin(s)	Short description
0	register	Signed	Register head & code for ID
1	force_register	Root	Force-register a Para Id
2	deregister	Root / para owner / para	Deregister a Para Id
3	swap	Root / para owner / para	Swap two parachains
4	remove_lock	Root / para	Remove manager lock
5	reserve	Signed	Reserve a new Para Id
6	add_lock	Root / para owner / para	Add manager lock
7	schedule_code_upgrade	Root / para owner / para	Schedule a code upgrade
8	set_current_head	Root / para owner / para	Set parachain current head

TODO

• Check subscan how they are used. Subscan calls to registrar.
• Get approval on interfaces for registrar-para and registrar-relay
• Any dApps using this?

Treat this as meta issue. Create sub-issues as needed.

User flows

Docs: https://docs.polkadot.com/parachains/launch-a-parachain/deploy-to-polkadot/
Abbreviations:

Old

• RC - Relay Chain (paras_registrar)

New

• CT - Coretime Chain (registrar_para)
• RC - Relay Chain (registrar_relay)

Reserve

Old flow

sequenceDiagram
    autonumber
    actor User
    participant RC

    User->>RC: registrar.reserve()
    activate RC
    RC->>RC: Hold ParaDeposit
    RC->>RC: Allow next para_id<br/>(counter lives on RC)
    RC-->>User: Ok(para_id)
    deactivate RC

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New flow

sequenceDiagram
    autonumber
    actor User
    participant CT 
    participant RC

    User->>CT: registrar_para.reserve()
    activate CT
    CT->>CT: Hold ParaDeposit
    CT->>CT: Insert Pending { who, deposit }
    CT-)RC: XCM Transact → registrar_relay.reserve()
    deactivate CT

    activate RC
    RC->>RC: Allot next para_id
    RC--)CT: Report result (para_id)
    deactivate RC

    activate CT
    CT->>CT: Pending → Reserved(para_id)
    CT-->>User: event ParaIdReserved(para_id)
    deactivate CT

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---

Register

Note: Before registering para id must be reserved with reserve

Old (current) flow

sequenceDiagram
    autonumber
    actor User
    participant RC

    User->>RC: register(id, genesis_head, validation_code)
    RC->>RC: validate code + head size, compute deposit
    RC->>RC: reserve extra deposit (or refund rebate)
    RC->>RC: schedule_para_initialize(id, genesis)
    RC-->>User: Registered { para_id, manager }

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New flow

sequenceDiagram
    autonumber
    actor User
    participant CT
    participant RC

    activate CT
    User->>CT: register(id, genesis_head, code_len, code_hash)
    CT->>CT: fast fail if para_id not registered
    CT->>CT: code size + head size, compute deposit
    CT->>CT: reserve deposit
    CT->>CT: Insert Pending { para_id, manager }
    CT->>RC: XCM (para_id, head, code_hash) to RC
    CT->>User: RegisterRequested { para_id, manager }
    deactivate CT

    User->>RC: register_code(id, validation_code) - unsigned extrinsic
    activate RC
    RC->>RC: validate code against hash and id (fast check) + pull genesis_head
    RC->>RC: paras_registrar(id, genesis_head, validation_code) (no reservations here)
    RC->>RC: clear storage
    RC->>CT: Registrar { id }
    deactivate RC

    activate CT
    CT->>CT: Insert Done { para_id, manager }
    CT->>User: Event Registrar { para_id, manager }
    deactivate CT

   

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