The approach is different from the one typically used. It is recommended to consult the person within your company which had the one hour free training session for the regular approach.
Regarding 429 errors, please consult:
to determine on what rate limiter is being exceeded.
Note that the table function TicketMessagesByTicketId is executed once for each and every ticket with filtering. For optimization it is in general not recommended to construct URLs in code unless the logic is fully understood of the UniversalSQL Engine and OData, but to use the advantages of “query folding”. OR-optimization is in general not available on database platforms.
There is no known efficient alternative to retrieve the body of all messages offered by Teamleader APIs.