[feature] Add domain limit DB model and API endpoints (#4554)

# 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 adds database models, (support) functions, migration, and API models + endpoints for upcoming domain limit functionality.

Part of https://codeberg.org/superseriousbusiness/gotosocial/issues/2676, https://codeberg.org/superseriousbusiness/gotosocial/issues/9, and https://codeberg.org/superseriousbusiness/gotosocial/issues/1730

## 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.
- [x] 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/4554
Co-authored-by: tobi <tobi.smethurst@protonmail.com>
Co-committed-by: tobi <tobi.smethurst@protonmail.com>

internal/api/util/scopes.go

@@ -34,6 +34,7 @@ const (
 	scopeCustomEmojis  = "custom_emojis"
 	scopeDomainAllows  = "domain_allows"
 	scopeDomainBlocks  = "domain_blocks"
+	scopeDomainLimits  = "domain_limits"
 	scopeFavourites    = "favourites"
 	scopeFilters       = "filters"
 	scopeFollows       = "follows"
@@ -92,6 +93,8 @@ const (
 	ScopeAdminWriteDomainAllows Scope = ScopeAdminWrite + ":" + scopeDomainAllows
 	ScopeAdminReadDomainBlocks  Scope = ScopeAdminRead + ":" + scopeDomainBlocks
 	ScopeAdminWriteDomainBlocks Scope = ScopeAdminWrite + ":" + scopeDomainBlocks
+	ScopeAdminReadDomainLimits  Scope = ScopeAdminRead + ":" + scopeDomainLimits
+	ScopeAdminWriteDomainLimits Scope = ScopeAdminWrite + ":" + scopeDomainLimits
 	ScopeAdminReadReports       Scope = ScopeAdminRead + ":" + scopeReports
 	ScopeAdminWriteReports      Scope = ScopeAdminWrite + ":" + scopeReports
 )