https://mattermost.atlassian.net/browse/MM-22051
```release-note
Removed the following methods/functions:
(ad *AccessData) ToJson()
(ar *AccessResponse) ToJson()
(ar *AnalyticsRow) ToJson()
(ar AnalyticsRows) ToJson()
(o *Audit) ToJson()
(o Audits) ToJson()
(ad *AuthData) ToJson()
(ar *AuthorizeRequest) ToJson()
(o *ChannelPatch) ToJson()
(o *ChannelsWithCount) ToJson()
(o *ChannelCounts) ToJson()
(o *ChannelData) ToJson()
(o *ChannelMembers) ToJson()
(o *ChannelUnread) ToJson()
(o *ChannelUnreadAt) ToJson()
(o *ChannelStats) ToJson()
(o *ChannelView) ToJson()
(o *ChannelViewResponse) ToJson()
(o *ClusterDiscovery) ToJson()
(ci *ClusterInfo) ToJson()
(cs *ClusterStats) ToJson()
(o *Command) ToJson()
CommandListToJson(l []*Command) string
(o *CommandArgs) ToJson()
(cmr *CommandMoveRequest) ToJson()
(o *CommandResponse) ToJson()
(c *Compliance) ToJson()
(c Compliances) ToJson()
(o *Config) ToJson()
EmojiListToJson(emojiList []*Emoji)
```
* Consistent license message for all the go files
* Fixing the last set of unconsistencies with the license headers
* Addressing PR review comments
* Fixing busy.go and busy_test.go license header
* Implement POST /oauth/apps endpoint for APIv4
* Implement GET /oauth/apps endpoint for APIv4
* Implement GET /oauth/apps/{app_id} and /oauth/apps/{app_id}/info endpoints for APIv4
* Refactor API version independent oauth endpoints
* Implement DELETE /oauth/apps/{app_id} endpoint for APIv4
* Implement /oauth/apps/{app_id}/regen_secret endpoint for APIv4
* Implement GET /user/{user_id}/oauth/apps/authorized endpoint for APIv4
* Implement POST /oauth/deauthorize endpoint
* PLT-3484 OAuth2 Service Provider
* PM text review for OAuth 2.0 Service Provider
* PLT-3484 OAuth2 Service Provider UI tweaks (#3668)
* Tweaks to help text
* Pushing OAuth improvements (#3680)
* Re-arrange System Console for OAuth 2.0 Provider
