resolutionist
/ˌrɛzəˈl(j)uːʃ(ə)nɪst/ /ˌrɛzəˈl(j)uːʃənɪst/noun
1A person who formulates or supports a resolution. Compare resolutioner. Now rare.
2A person who makes a (New Year's) resolution.
Origin
Early 19th century. From resolution + -ist. Compare earlier resolutioner.