isRegionValid

Determines if the given region is valid for the purposes of endpoint lookup, specifically that the region is suitable to use in a URI hostname according to RFC 3986 § 3.2.2.

Valid characters for regions include:

• URI unreserved characters:

• Uppercase letters (A through Z)

• Lowercase letters (a through z)

• Digits (0 through 9)

• Hyphen (-)

• Period/dot (.)

• Tilde (~)

• Underscore (_)

• Percent (%)

• URI sub-delimiters

• Ampersand (&)

• Apostrophe (')

• Asterisk (*)

• Comma (,)

• Dollar sign ($)

• Equals sign (=)

• Exclamation point (!)

• Parentheses (( and ))

• Plus (+)

• Semicolon (;)

Notable characters which are invalid for regions include:

• Space ()

• At sign (@)

• Backtick/grave (` ` `)

• Braces ({ and })

• Brackets ([ and ])

• Caret (^)

• Colon (:)

• Double quote (")

• Hash/number sign (#)

• Inequality signs (< and >)

• Pipe (|)

• Question mark (?)

• Slashes (/ and \)

• All non-ASCII characters (e.g., Unicode characters)