feat(app,api): let group DM owners allow mature content (#3350)

fluxer_api/src/api/openapi/openapi.json

@@ -32324,6 +32324,10 @@
 							"nicks": {
 								"description": "Custom nicknames for users in this group DM",
 								"anyOf": [{"$ref": "#/components/schemas/ChannelNicknameOverrides"}, {"type": "null"}]
+							},
+							"nsfw": {
+								"description": "Whether the group DM is marked for mature content (owner only)",
+								"type": ["boolean", "null"]
 							}
 						}
 					},
@@ -39725,6 +39729,7 @@
 					"MAX_GROUP_DM_RECIPIENTS",
 					"MAX_GROUP_DMS",
 					"GROUP_DM_RECIPIENTS_NOT_ADDABLE",
+					"GROUP_DM_MATURE_CONTENT_INELIGIBLE",
 					"MAX_GUILD_CHANNELS",
 					"MAX_GUILD_MEMBERS",
 					"MAX_GUILD_ROLES",
@@ -40021,6 +40026,7 @@
 					"You've reached the maximum of {count, plural, one {# group DM recipient} other {# group DM recipients}}.",
 					"You've reached the maximum of {count, plural, one {# group DM} other {# group DMs}}.",
 					"One or more selected users can't be added to this group DM.",
+					"Not everyone in this group is eligible for mature content.",
 					"You've reached the maximum of {count, plural, one {# community channel} other {# community channels}}.",
 					"You've reached the maximum of {count, plural, one {# community member} other {# community members}}.",
 					"You've reached the maximum of {count, plural, one {# community role} other {# community roles}}.",