[feature] Implement following hashtags (#3141)

* Implement followed tags API

* Insert statuses with followed tags into home timelines

* Test following and unfollowing tags

* Correct Swagger path params

* Trim conversation caches

* Migration for followed_tags table

* Followed tag caches and DB implementation

* Lint and tests

* Add missing tag info endpoint, reorganize tag API

* Unwrap boosts when timelining based on tags

* Apply visibility filters to tag followers

* Address review comments

internal/api/model/tag.go

@@ -31,4 +31,7 @@ type Tag struct {
 	// Currently just a stub, if provided will always be an empty array.
 	// example: []
 	History *[]any `json:"history,omitempty"`
+	// Following is true if the user is following this tag, false if they're not,
+	// and not present if there is no currently authenticated user.
+	Following *bool `json:"following,omitempty"`
 }