Hello,
To start, I am not an Avaya developer. I am posting this after I did not manage to get anyone to do the integration.

Anyone can recommend a company or a freelancer that can do RESTful APIs integrations with Avaya API office v2 500.

I suppose that the APIs on these two links can meet my requirements below:

https://www.devconnectprogram.com/site/global/products_resources/ip_office/interfaces/centralized_cti_web_services/overview/index.gsp

https://www.devconnectprogram.com/site/global/products_resources/ip_office/interfaces/index.gsp .




1- Once the phone rings, you call a RESTful POST / GET Web Serice API to pass:
INCIDENT_ID -- I suppose that Avaya generates an ID for each call.
COUNTRY_CODE
CALLER_ID
CALLED_DID ( Requested) DID
EXTENSION ( Requested)
CALL_TIME (The exact time of receiving the call)
PBX_ID (Hardcoded Value)
To an API:
e.g,

DOMAIN-URL/[INCIDENT_ID}/{COUNTRY_CODE}/{CALLER_ID}/{CALLED_DID}/{EXTENSION}/{CALL_TIME}/{PBX_ID}

2- Once the phone is Picked Up, pass:
INCIDENT_ID
COUNTRY_CODE
CALLER_ID
CALLED_DID (Requested) DID
EXTENSION --- that picked up the call
CALL_TIME (The exact time of receiving the call)
PICKUP_TIME
PBX_ID (Hardcoded Value)

3- Once the phone is Dropped pass:
CALL_TYPE ( IN / OUT)
INCIDENT_ID
COUNTRY_CODE
CALLER_ID
CALLED_DID
EXTENSION
CALL_DURATION (in seconds) --- I suppose pass 0 in case the call was missed.
RECORDING_FILE_PATH. (In case the recording is set up.)
PBX_ID (Hardcoded Value)

We need to discuss the options of:
The call is answered by the Auto Reply msg.
The call is forwarded.
The call reaches a DID that has a rule to Auto forward to a mobile phone number. (Usually after working hours / holidays)