Parse key=value pairs

Write a function `parse_key_value_pairs(text)` that takes a string containing zero or more space-separated `key=value` pairs and returns a dictionary mapping keys to values as strings. Rules: - Pairs are separated by one or more spaces. - Each pair consists of a key and a value separated by the first `=`. - Keys and values contain no spaces (values may be quoted to include spaces). - If a value is surrounded by double quotes (`"`), the quotes are removed and the value may contain spaces. A quoted value is always the last token in its pair; i.e., no additional `key=value` follows it within the same pair. An empty quoted value is valid and becomes an empty string. - Keys are not quoted. Keys may contain alphanumeric characters and underscores. If a key appears multiple times, the last occurrence wins. - If text is empty or contains no valid `key=value` pairs, return an empty dictionary. - You do not need to handle escaped quotes or nested quotes. Implement the function exactly as described. The returned dictionary should have string keys and string values.

>>> parse_key_value_pairs("name=Alice age=30")
{'name': 'Alice', 'age': '30'}

>>> parse_key_value_pairs("greeting=\"Hello world\" lang=en")
{'greeting': 'Hello world', 'lang': 'en'}

>>> parse_key_value_pairs("")
{}

>>> parse_key_value_pairs("color=\"blue sky\"")
{'color': 'blue sky'}

>>> parse_key_value_pairs("empty=\"\" key=value")
{'empty': '', 'key': 'value'}