fix: Use tuples for pkey check

[SpaceCondor]

target-postgres/target_postgres/sinks.py

Lines 161 to 169 in d07b415

	for record in records:
	insert_record = {
	column.name: record.get(column.name) for column in columns
	}
	# No need to check for a KeyError here because the SDK already
	# guarantees that all key properties exist in the record.
	primary_key_value = "".join([str(record[key]) for key in primary_keys])
	insert_records[primary_key_value] = insert_record
	data_to_insert = list(insert_records.values())

Currently the code above uses string concatenation to check for duplicate primary key values, however this is problematic since the records below will be treated as the same record and the first will be omitted:

Record 1:

• Primary Key 1: AB
• Primary Key 2: C

Record 2:

• Primary Key 1: A
• Primary Key 2: BC

Changing to a tuple should mitigate this.

[edgarrmondragon]

hmm tests are no longer running on PRs from forks...

Nevermind: #447

[edgarrmondragon]

Thanks @SpaceCondor!