Support repo license (#24872)

Close #278
Close #24076

## Solutions:
- Use
[google/licenseclassifier](https://github.com/google/licenseclassifier/)
Test result between
[google/licensecheck](https://github.com/google/licensecheck) and
[go-license-detector](https://github.com/go-enry/go-license-detector):
https://github.com/go-gitea/gitea/pull/24872#issuecomment-1560361167
Test result between
[google/licensecheck](https://github.com/google/licensecheck) and
[google/licenseclassifier](https://github.com/google/licenseclassifier/):
https://github.com/go-gitea/gitea/pull/24872#issuecomment-1576092178
- Generate License Convert Name List to avoid import license templates
with same contents
Gitea automatically get latest license data from[
spdx/license-list-data](https://github.com/spdx/license-list-data).
But unfortunately, some license templates have same contents. #20915
[click here to see the
list](https://github.com/go-gitea/gitea/pull/24872#issuecomment-1584141684)
So we will generate a list of these license templates with same contents
and create a new file to save the result when using `make
generate-license`. (Need to decide the save path)
- Save License info into a new table `repo_license`
Can easily support searching repo by license in the future.

## Screen shot
Single License:

![image](https://github.com/go-gitea/gitea/assets/18380374/41260bd7-0b4c-4038-8592-508706cffa9f)

Multiple Licenses:

![image](https://github.com/go-gitea/gitea/assets/18380374/34ce2f73-7e18-446b-9b96-ecc4fb61bd70)

Triggers:
- [x] Push commit to default branch
- [x] Create repo
- [x] Mirror repo
- [x] When Default Branch is changed, licenses should be updated

Todo:
- [x] Save Licenses info in to DB when there's a change to license file
in the commit
- [x] DB Migration
- [x] A nominal test?
- [x] Select which library to
use(https://github.com/go-gitea/gitea/pull/24872#issuecomment-1560361167)
- [x] API Support
- [x] Add repo license table
- ~Select license in settings if there are several licenses(Not
recommended)~
- License board(later, not in this PR)

![image](https://github.com/go-gitea/gitea/assets/18380374/2c3c3bf8-bcc2-4c6d-8ce0-81d1a9733878)

---------

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Denys Konovalov <kontakt@denyskon.de>
Co-authored-by: delvh <dev.lh@web.de>
Co-authored-by: KN4CK3R <admin@oldschoolhack.me>
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: 6543 <m.huber@kithara.com>
Co-authored-by: a1012112796 <1012112796@qq.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.com>

templates/repo/sub_menu.tmpl

@@ -13,7 +13,12 @@
 					{{svg "octicon-tag"}} <b>{{ctx.Locale.PrettyNumber .NumTags}}</b> {{ctx.Locale.TrN .NumTags "repo.tag" "repo.tags"}}
 				</a>
 			{{end}}
-			<span class="item not-mobile" {{if not (eq .Repository.Size 0)}}data-tooltip-content="{{.Repository.SizeDetailsString}}"{{end}}>
+			{{if .DetectedRepoLicenses}}
+				<a class="item muted" href="{{.RepoLink}}/src/{{.Repository.DefaultBranch}}/{{PathEscapeSegments .LicenseFileName}}" data-tooltip-placement="top" data-tooltip-content="{{StringUtils.Join .DetectedRepoLicenses ", "}}">
+					{{svg "octicon-law"}} <b>{{if eq (len .DetectedRepoLicenses) 1}}{{index .DetectedRepoLicenses 0}}{{else}}{{ctx.Locale.Tr "repo.multiple_licenses"}}{{end}}</b>
+				</a>
+			{{end}}
+			<span class="item not-mobile" {{if not (eq .Repository.Size 0)}}data-tooltip-placement="top" data-tooltip-content="{{.Repository.SizeDetailsString}}"{{end}}>
 				{{$fileSizeFormatted := FileSize .Repository.Size}}{{/* the formatted string is always "{val} {unit}" */}}
 				{{$fileSizeFields := StringUtils.Split $fileSizeFormatted " "}}
 				{{svg "octicon-database"}} <b>{{ctx.Locale.PrettyNumber (index $fileSizeFields 0)}}</b> {{index $fileSizeFields 1}}

templates/swagger/v1_json.tmpl

@@ -10640,6 +10640,42 @@
         }
       }
     },
+    "/repos/{owner}/{repo}/licenses": {
+      "get": {
+        "produces": [
+          "application/json"
+        ],
+        "tags": [
+          "repository"
+        ],
+        "summary": "Get repo licenses",
+        "operationId": "repoGetLicenses",
+        "parameters": [
+          {
+            "type": "string",
+            "description": "owner of the repo",
+            "name": "owner",
+            "in": "path",
+            "required": true
+          },
+          {
+            "type": "string",
+            "description": "name of the repo",
+            "name": "repo",
+            "in": "path",
+            "required": true
+          }
+        ],
+        "responses": {
+          "200": {
+            "$ref": "#/responses/LicensesList"
+          },
+          "404": {
+            "$ref": "#/responses/notFound"
+          }
+        }
+      }
+    },
     "/repos/{owner}/{repo}/media/{filepath}": {
       "get": {
         "produces": [
@@ -24142,6 +24178,13 @@
           "type": "string",
           "x-go-name": "LanguagesURL"
         },
+        "licenses": {
+          "type": "array",
+          "items": {
+            "type": "string"
+          },
+          "x-go-name": "Licenses"
+        },
         "link": {
           "type": "string",
           "x-go-name": "Link"
@@ -25717,6 +25760,15 @@
         }
       }
     },
+    "LicensesList": {
+      "description": "LicensesList",
+      "schema": {
+        "type": "array",
+        "items": {
+          "type": "string"
+        }
+      }
+    },
     "MarkdownRender": {
       "description": "MarkdownRender is a rendered markdown document",
       "schema": {