[feature] Hashtag federation (in/out), hashtag client API endpoints (#2032)

* update go-fed

* do the things

* remove unused columns from tags

* update to latest lingo from main

* further tag shenanigans

* serve stub page at tag endpoint

* we did it lads

* tests, oh tests, ohhh tests, oh tests (doo doo doo doo)

* swagger docs

* document hashtag usage + federation

* instanceGet

* don't bother parsing tag href

* rename whereStartsWith -> whereStartsLike

* remove GetOrCreateTag

* dont cache status tag timelineability

internal/db/bundb/util.go

@@ -34,9 +34,10 @@ var likeEscaper = strings.NewReplacer(
 	`_`, `\_`, // Exactly one char.
 )
 
-// whereSubqueryLike appends a WHERE clause to the
-// given SelectQuery, which searches for matches
-// of `search` in the given subQuery using LIKE.
+// whereLike appends a WHERE clause to the
+// given SelectQuery, which searches for
+// matches of `search` in the given subQuery
+// using LIKE.
 func whereLike(
 	query *bun.SelectQuery,
 	subject interface{},
@@ -58,6 +59,30 @@ func whereLike(
 	)
 }
 
+// whereStartsLike is like whereLike,
+// but only searches for strings that
+// START WITH `search`.
+func whereStartsLike(
+	query *bun.SelectQuery,
+	subject interface{},
+	search string,
+) *bun.SelectQuery {
+	// Escape existing wildcard + escape
+	// chars in the search query string.
+	search = likeEscaper.Replace(search)
+
+	// Add our own wildcards back in; search
+	// zero or more chars after the query.
+	search += `%`
+
+	// Append resulting WHERE
+	// clause to the main query.
+	return query.Where(
+		"(?) LIKE ? ESCAPE ?",
+		subject, search, `\`,
+	)
+}
+
 // updateWhere parses []db.Where and adds it to the given update query.
 func updateWhere(q *bun.UpdateQuery, where []db.Where) {
 	for _, w := range where {