Should resolve #30642.

Before this commit, we were treating an empty `?sort=` query parameter
as the correct sorting type (which is to sort issues in descending order
by their created UNIX time). But when we perform `sort=latest`, we did
not include this as a type so we would sort by the most recently updated
when reaching the `default` switch statement block.

This commit fixes this by considering the empty string, "latest", and
just any other string that is not mentioned in the switch statement as
sorting by newest.

Signed-off-by: 6543 <6543@obermui.de>

It will fix #28268 .

<img width="1313" alt="image"
src="https://github.com/go-gitea/gitea/assets/9418365/cb1e07d5-7a12-4691-a054-8278ba255bfc">

<img width="1318" alt="image"
src="https://github.com/go-gitea/gitea/assets/9418365/4fd60820-97f1-4c2c-a233-d3671a5039e9">

## :warning: BREAKING :warning:

But need to give up some features:

<img width="1312" alt="image"
src="https://github.com/go-gitea/gitea/assets/9418365/281c0d51-0e7d-473f-bbed-216e2f645610">

However, such abandonment may fix #28055 .

## Backgroud

When the user switches the dashboard context to an org, it means they
want to search issues in the repos that belong to the org. However, when
they switch to themselves, it means all repos they can access because
they may have created an issue in a public repo that they don't own.

<img width="286" alt="image"
src="https://github.com/go-gitea/gitea/assets/9418365/182dcd5b-1c20-4725-93af-96e8dfae5b97">

It's a confusing design. Think about this: What does "In your
repositories" mean when the user switches to an org? Repos belong to the
user or the org?

Whatever, it has been broken by #26012 and its following PRs. After the
PR, it searches for issues in repos that the dashboard context user owns
or has been explicitly granted access to, so it causes #28268.

## How to fix it

It's not really difficult to fix it. Just extend the repo scope to
search issues when the dashboard context user is the doer. Since the
user may create issues or be mentioned in any public repo, we can just
set `AllPublic` to true, which is already supported by indexers. The DB
condition will also support it in this PR.

But the real difficulty is how to count the search results grouped by
repos. It's something like "search issues with this keyword and those
filters, and return the total number and the top results. **Then, group
all of them by repo and return the counts of each group.**"

<img width="314" alt="image"
src="https://github.com/go-gitea/gitea/assets/9418365/5206eb20-f8f5-49b9-b45a-1be2fcf679f4">

Before #26012, it was being done in the DB, but it caused the results to
be incomplete (see the description of #26012).

And to keep this, #26012 implement it in an inefficient way, just count
the issues by repo one by one, so it cannot work when `AllPublic` is
true because it's almost impossible to do this for all public repos.


1bfcdeef4c/modules/indexer/issues/indexer.go (L318-L338)

## Give up unnecessary features

We may can resovle `TODO: use "group by" of the indexer engines to
implement it`, I'm sure it can be done with Elasticsearch, but IIRC,
Bleve and Meilisearch don't support "group by".

And the real question is, does it worth it? Why should we need to know
the counts grouped by repos?

Let me show you my search dashboard on gitea.com.

<img width="1304" alt="image"
src="https://github.com/go-gitea/gitea/assets/9418365/2bca2d46-6c71-4de1-94cb-0c9af27c62ff">

I never think the long repo list helps anything.

And if we agree to abandon it, things will be much easier. That is this
PR.

## TODO

I know it's important to filter by repos when searching issues. However,
it shouldn't be the way we have it now. It could be implemented like
this.

<img width="1316" alt="image"
src="https://github.com/go-gitea/gitea/assets/9418365/99ee5f21-cbb5-4dfe-914d-cb796cb79fbe">

The indexers support it well now, but it requires some frontend work,
which I'm not good at. So, I think someone could help do that in another
PR and merge this one to fix the bug first.

Or please block this PR and help to complete it.

Finally, "Switch dashboard context" is also a design that needs
improvement. In my opinion, it can be accomplished by adding filtering
conditions instead of "switching".

Follow #26012 #26490.

A detailed description has been added to the comment.

related: #26012

### Bugs
1. missing project filter on the issue page.

1e76a824bc/modules/indexer/issues/dboptions.go (L11-L15)
3. incorrect SQL condition: some issue does not belong to a project but
exists on the project_issue table.

f5dbac9d36/models/issues/issue_search.go (L233)

### Before:

![before](https://github.com/go-gitea/gitea/assets/50507092/1dcde39e-3e2f-4151-b2c6-4d67bf493c2f)

### After:

![after](https://github.com/go-gitea/gitea/assets/50507092/badfb81f-056d-4a2f-9838-1cba9c15768d)

---------

Co-authored-by: Giteabot <teabot@gitea.io>

Fix #24662.

Replace #24822 and #25708 (although it has been merged)


## Background

In the past, Gitea supported issue searching with a keyword and
conditions in a less efficient way. It worked by searching for issues
with the keyword and obtaining limited IDs (as it is heavy to get all)
on the indexer (bleve/elasticsearch/meilisearch), and then querying with
conditions on the database to find a subset of the found IDs. This is
why the results could be incomplete.

To solve this issue, we need to store all fields that could be used as
conditions in the indexer and support both keyword and additional
conditions when searching with the indexer.

## Major changes

- Redefine `IndexerData` to include all fields that could be used as
filter conditions.
- Refactor `Search(ctx context.Context, kw string, repoIDs []int64,
limit, start int, state string)` to `Search(ctx context.Context, options
*SearchOptions)`, so it supports more conditions now.
- Change the data type stored in `issueIndexerQueue`. Use
`IndexerMetadata` instead of `IndexerData` in case the data has been
updated while it is in the queue. This also reduces the storage size of
the queue.
- Enhance searching with Bleve/Elasticsearch/Meilisearch, make them
fully support `SearchOptions`. Also, update the data versions.
- Keep most logic of database indexer, but remove
`issues.SearchIssueIDsByKeyword` in `models` to avoid confusion where is
the entry point to search issues.
- Start a Meilisearch instance to test it in unit tests.
- Add unit tests with almost full coverage to test
Bleve/Elasticsearch/Meilisearch indexer.

---------

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>