add --read-only and --maintenance program option

Signed-off-by: Jason Volk <jason@zemos.net>

Cargo.toml

@@ -892,6 +892,7 @@ needless_continue = { level = "allow", priority = 1 }
 no_effect_underscore_binding = { level = "allow", priority = 1 }
 similar_names = { level = "allow", priority = 1 }
 single_match_else = { level = "allow", priority = 1 }
+struct_excessive_bools = { level = "allow", priority = 1 }
 struct_field_names = { level = "allow", priority = 1 }
 unnecessary_wraps = { level = "allow", priority = 1 }
 unused_async = { level = "allow", priority = 1 }