Relay Agent helper: add support for source, hostname, and network instance

[rachidtt]

This is a follow-up and update to #964 #951 . More context can be found there

Change Scope

• Replace “helper-address” leaf-list with keyed list
• Update address type to be oc:inet:host to support ip and hostname configuration
• Add support for source-interface or source-address configuration
• Add option to specify network-instance
• This change is backwards compatible

Platform Implementations

• Arista: ip helper-address

New tree (relevant changes):

  +--rw relay-agent
     +--rw dhcp
     |  +--rw interfaces
     |     +--rw interface* [id]
     |        +--rw id                          -> ../config/id
     |        +--rw config
     |        |  +--rw id?                 oc-if:interface-id
     |        |  +--rw enable?             boolean
     |        |  x--rw helper-address*     inet:ip-address
     |        |  +--rw helper-addresses
     |        |     +--rw helper-address* [address]
     |        |        +--rw address    -> ../config/address
     |        |        +--rw config
     |        |        |  +--rw address?            oc-inet:host
     |        |        |  +--rw local-address?      union
     |        |        |  +--rw network-instance?   oc-ni:network-instance-ref
     |        |        +--ro state
     |        |           +--ro address?            oc-inet:host
     |        |           +--ro local-address?      union
     |        |           +--ro network-instance?   oc-ni:network-instance-ref
     |        +--ro state
     |        |  +--ro id?                 oc-if:interface-id
     |        |  +--ro enable?             boolean
     |        |  x--ro helper-address*     inet:ip-address
     |        |  +--ro helper-addresses
     |        |  |  +--ro helper-address* [address]
     |        |  |     +--ro address    -> ../config/address
     |        |  |     +--ro config
     |        |  |     |  +--ro address?            oc-inet:host
     |        |  |     |  +--ro local-address?      union
     |        |  |     |  +--ro network-instance?   oc-ni:network-instance-ref
     |        |  |     +--ro state
     |        |  |        +--ro address?            oc-inet:host
     |        |  |        +--ro local-address?      union
     |        |  |        +--ro network-instance?   oc-ni:network-instance-ref
     +--rw dhcpv6
        +--rw interfaces
           +--rw interface* [id]
              +--rw id               -> ../config/id
              +--rw config
              |  +--rw id?                 oc-if:interface-id
              |  +--rw enable?             boolean
              |  x--rw helper-address*     inet:ipv6-address
              |  +--rw helper-addresses
              |     +--rw helper-address* [address]
              |        +--rw address    -> ../config/address
              |        +--rw config
              |        |  +--rw address?            oc-inet:host
              |        |  +--rw local-address?      union
              |        |  +--rw network-instance?   oc-ni:network-instance-ref
              |        +--ro state
              |           +--ro address?            oc-inet:host
              |           +--ro local-address?      union
              |           +--ro network-instance?   oc-ni:network-instance-ref
              +--ro state
              |  +--ro id?                 oc-if:interface-id
              |  +--ro enable?             boolean
              |  x--ro helper-address*     inet:ipv6-address
              |  +--ro helper-addresses
              |  |  +--ro helper-address* [address]
              |  |     +--ro address    -> ../config/address
              |  |     +--ro config
              |  |     |  +--ro address?            oc-inet:host
              |  |     |  +--ro local-address?      union
              |  |     |  +--ro network-instance?   oc-ni:network-instance-ref
              |  |     +--ro state
              |  |        +--ro address?            oc-inet:host
              |  |        +--ro local-address?      union
              |  |        +--ro network-instance?   oc-ni:network-instance-ref```

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[dplore]

/gcbrun

[OpenConfigBot]

No major YANG version changes in commit e4a7ce8

[dplore]

One minor change suggested. Also, check the linter output. There needs to be a config and state container, and the config container must have config set to true.

Ref: https://gist.github.com/OpenConfigBot/0d4b55defd09566d4bd0bebb7efeb460