[feature] Stub out trends + suggestions (always return empty array) (#4435)

# Description

> If this is a code change, please include a summary of what you've coded, and link to the issue(s) it closes/implements.
>
> If this is a documentation change, please briefly describe what you've changed and why.

This pull request stubs out the trends and suggestions APIs, just returning empty arrays for all four of the added endpoints. This is to help clients show fewer errors. It does *not* signal any intention to actually implement these endpoints properly, though you never know.

closes https://codeberg.org/superseriousbusiness/gotosocial/issues/4385

## Checklist

Please put an x inside each checkbox to indicate that you've read and followed it: `[ ]` -> `[x]`

If this is a documentation change, only the first checkbox must be filled (you can delete the others if you want).

- [x] I/we have read the [GoToSocial contribution guidelines](https://codeberg.org/superseriousbusiness/gotosocial/src/branch/main/CONTRIBUTING.md).
- [x] I/we have discussed the proposed changes already, either in an issue on the repository, or in the Matrix chat.
- [x] I/we have not leveraged AI to create the proposed changes.
- [x] I/we have performed a self-review of added code.
- [x] I/we have written code that is legible and maintainable by others.
- [x] I/we have commented the added code, particularly in hard-to-understand areas.
- [x] I/we have made any necessary changes to documentation.
- [ ] I/we have added tests that cover new code.
- [x] I/we have run tests and they pass locally with the changes.
- [x] I/we have run `go fmt ./...` and `golangci-lint run`.

Reviewed-on: https://codeberg.org/superseriousbusiness/gotosocial/pulls/4435
Co-authored-by: tobi <tobi.smethurst@protonmail.com>
Co-committed-by: tobi <tobi.smethurst@protonmail.com>

internal/api/client.go

@@ -52,9 +52,11 @@ import (
 	"code.superseriousbusiness.org/gotosocial/internal/api/client/search"
 	"code.superseriousbusiness.org/gotosocial/internal/api/client/statuses"
 	"code.superseriousbusiness.org/gotosocial/internal/api/client/streaming"
+	"code.superseriousbusiness.org/gotosocial/internal/api/client/suggestions"
 	"code.superseriousbusiness.org/gotosocial/internal/api/client/tags"
 	"code.superseriousbusiness.org/gotosocial/internal/api/client/timelines"
 	"code.superseriousbusiness.org/gotosocial/internal/api/client/tokens"
+	"code.superseriousbusiness.org/gotosocial/internal/api/client/trends"
 	"code.superseriousbusiness.org/gotosocial/internal/api/client/user"
 	"code.superseriousbusiness.org/gotosocial/internal/db"
 	"code.superseriousbusiness.org/gotosocial/internal/middleware"
@@ -100,9 +102,11 @@ type Client struct {
 	search              *search.Module              // api/v1/search, api/v2/search
 	statuses            *statuses.Module            // api/v1/statuses
 	streaming           *streaming.Module           // api/v1/streaming
+	suggestions         *suggestions.Module         // api/v2/suggestions
 	tags                *tags.Module                // api/v1/tags
 	timelines           *timelines.Module           // api/v1/timelines
 	tokens              *tokens.Module              // api/v1/tokens
+	trends              *trends.Module              // api/v1/trends
 	user                *user.Module                // api/v1/user
 }
 
@@ -155,9 +159,11 @@ func (c *Client) Route(r *router.Router, m ...gin.HandlerFunc) {
 	c.search.Route(h)
 	c.statuses.Route(h)
 	c.streaming.Route(h)
+	c.suggestions.Route(h)
 	c.tags.Route(h)
 	c.timelines.Route(h)
 	c.tokens.Route(h)
+	c.trends.Route(h)
 	c.user.Route(h)
 }
 
@@ -198,9 +204,11 @@ func NewClient(state *state.State, p *processing.Processor) *Client {
 		search:              search.New(p),
 		statuses:            statuses.New(p),
 		streaming:           streaming.New(p, time.Second*30, 4096),
+		suggestions:         suggestions.New(p),
 		tags:                tags.New(p),
 		timelines:           timelines.New(p),
 		tokens:              tokens.New(p),
+		trends:              trends.New(p),
 		user:                user.New(p),
 	}
 }