Massive rework of platform layer user/organization

The goal of this rework is to make it so I can pass around platform.User
instead of a pair of models.Organization and models.User. This is useful
for reason I kind of forget now, but it started with working on
notifications and ballooned massively from there into refactoring a
number of things that were bugging me.

This also includes a tiny amount of work on server-side events (SSE).

 * background stuff lives inside the platform now, which I need for
   having it push updates through SSE
 * userfile now lives in the platform, under file, so other platform
   functions can safely use it
 * oauth is broken into pieces and inside platform because other stuff
   was calling it already, but badly.
 * notifications go into the platform as well

userfile/upload.go

@@ -1,76 +0,0 @@
-package userfile
-
-import (
-	"bytes"
-	"fmt"
-	"io"
-	"mime/multipart"
-	"net/http"
-
-	"github.com/google/uuid"
-	"github.com/rs/zerolog/log"
-)
-
-type FileUpload struct {
-	ContentType string
-	Name        string
-	SizeBytes   int
-	UUID        uuid.UUID
-}
-
-func SaveFileUpload(r *http.Request, name string, collection Collection) ([]FileUpload, error) {
-	results := make([]FileUpload, 0)
-	for n, fheaders := range r.MultipartForm.File {
-		log.Debug().Str("n", n).Msg("looking at header")
-		if n != name {
-			continue
-		}
-		for _, headers := range fheaders {
-			f, err := saveFileUpload(headers, collection)
-			if err != nil {
-				return results, fmt.Errorf("Failed to extract photo upload: %w", err)
-			}
-			results = append(results, f)
-		}
-	}
-	return results, nil
-}
-func saveFileUploads(r *http.Request, collection Collection) ([]FileUpload, error) {
-	results := make([]FileUpload, 0)
-	for name, fheaders := range r.MultipartForm.File {
-		for _, headers := range fheaders {
-			upload, err := saveFileUpload(headers, collection)
-			if err != nil {
-				return results, fmt.Errorf("Failed to save upload '%s': %w", name, err)
-			}
-			results = append(results, upload)
-		}
-	}
-	return results, nil
-}
-func saveFileUpload(headers *multipart.FileHeader, collection Collection) (upload FileUpload, err error) {
-	file, err := headers.Open()
-	if err != nil {
-		return upload, fmt.Errorf("Failed to open header: %w", err)
-	}
-	defer file.Close()
-
-	file_bytes, err := io.ReadAll(file)
-	content_type := http.DetectContentType(file_bytes)
-
-	u, err := uuid.NewUUID()
-	if err != nil {
-		return upload, fmt.Errorf("Failed to create uuid", err)
-	}
-	err = FileContentWrite(bytes.NewReader(file_bytes), collection, u)
-	if err != nil {
-		return upload, fmt.Errorf("Failed to write file to disk: %w", err)
-	}
-	log.Info().Int("size", len(file_bytes)).Str("uploaded_filename", headers.Filename).Str("content-type", content_type).Str("uuid", u.String()).Msg("Saved an uploaded file to disk")
-	return FileUpload{
-		ContentType: content_type,
-		Name:        headers.Filename,
-		SizeBytes:   len(file_bytes),
-		UUID:        u,
-	}, nil
-}