Add page to create new letter branding

This has a form with 3 fields - the file upload field, logo name, and an
optional logo domain. Logos need to be uploaded in `.svg` format and we
then convert this to `.png` format and upload both file types to S3 as
well as saving the letter branding details in the database.

app/s3_client/s3_logo_client.py

@@ -6,6 +6,9 @@ from notifications_utils.s3 import s3upload as utils_s3upload
 
 TEMP_TAG = 'temp-{user_id}_'
 EMAIL_LOGO_LOCATION_STRUCTURE = '{temp}{unique_id}-{filename}'
+LETTER_PREFIX = 'letters/static/images/letter-template/'
+LETTER_TEMP_TAG = LETTER_PREFIX + TEMP_TAG
+LETTER_TEMP_LOGO_LOCATION = 'letters/static/images/letter-template/temp-{user_id}_{unique_id}-{filename}'
 
 
 def get_s3_object(bucket_name, filename):
@@ -33,10 +36,14 @@ def get_s3_objects_filter_by_prefix(prefix):
     return s3.Bucket(bucket_name).objects.filter(Prefix=prefix)
 
 
-def get_temp_truncated_email_filename(filename, user_id):
+def get_temp_truncated_filename(filename, user_id):
     return filename[len(TEMP_TAG.format(user_id=user_id)):]
 
 
+def get_letter_filename_with_no_path_or_extension(filename):
+    return filename[len(LETTER_PREFIX):-4]
+
+
 def upload_email_logo(filename, filedata, region, user_id):
     upload_file_name = EMAIL_LOGO_LOCATION_STRUCTURE.format(
         temp=TEMP_TAG.format(user_id=user_id),
@@ -55,20 +62,74 @@ def upload_email_logo(filename, filedata, region, user_id):
     return upload_file_name
 
 
+def upload_letter_temp_logo(filename, filedata, region, user_id):
+    upload_filename = LETTER_TEMP_LOGO_LOCATION.format(
+        user_id=user_id,
+        unique_id=str(uuid.uuid4()),
+        filename=filename
+    )
+    bucket_name = current_app.config['LOGO_UPLOAD_BUCKET_NAME']
+    utils_s3upload(
+        filedata=filedata,
+        region=region,
+        bucket_name=bucket_name,
+        file_location=upload_filename,
+        content_type='image/svg+xml'
+    )
+
+    return upload_filename
+
+
+def upload_letter_png_logo(filename, filedata, region):
+    bucket_name = current_app.config['LOGO_UPLOAD_BUCKET_NAME']
+    utils_s3upload(
+        filedata=filedata,
+        region=region,
+        bucket_name=bucket_name,
+        file_location=filename,
+        content_type='image/png'
+    )
+
+
 def permanent_email_logo_name(filename, user_id):
     if filename.startswith(TEMP_TAG.format(user_id=user_id)):
-        return get_temp_truncated_email_filename(filename=filename, user_id=user_id)
+        return get_temp_truncated_filename(filename=filename, user_id=user_id)
     else:
         return filename
 
 
+def permanent_letter_logo_name(filename, extension):
+    return LETTER_PREFIX + filename + '.' + extension
+
+
+def letter_filename_for_db(filename, user_id):
+    filename = get_letter_filename_with_no_path_or_extension(filename)
+
+    if filename.startswith(TEMP_TAG.format(user_id=user_id)):
+        filename = get_temp_truncated_filename(filename=filename, user_id=user_id)
+
+    return filename
+
+
 def delete_email_temp_files_created_by(user_id):
     for obj in get_s3_objects_filter_by_prefix(TEMP_TAG.format(user_id=user_id)):
         delete_s3_object(obj.key)
 
 
+def delete_letter_temp_files_created_by(user_id):
+    for obj in get_s3_objects_filter_by_prefix(LETTER_TEMP_TAG.format(user_id=user_id)):
+        delete_s3_object(obj.key)
+
+
 def delete_email_temp_file(filename):
     if not filename.startswith(TEMP_TAG[:5]):
         raise ValueError('Not a temp file: {}'.format(filename))
 
     delete_s3_object(filename)
+
+
+def delete_letter_temp_file(filename):
+    if not filename.startswith(LETTER_TEMP_TAG[:43]):
+        raise ValueError('Not a temp file: {}'.format(filename))
+
+    delete_s3_object(filename)